The following is very much a first pass at the profession. Feel free to notify me of anything that would be useful. Sorry for placeholders for pics, they will be added to soon.
UPDATED - Max number of Fragments per Cache is 3 (slvl 75-525). Dig Sites in Hyjal/Uldum count towards your 4 in Kalimdor, Twilight Highlands Dig Sites are part of your 4 for Eastern Kingdoms.
UPDATE 2 - Dealing with bugged Dig-site (see Troubleshooting)
UPDATED 3 - 14/12/2010 Hotfix: Fragment Caches can contain between 3 and 6 Fragments rather than just 3
UPDATED 4 - Daily quests for buffs in 5-man dungeons have been in the game for some time, requiring a race's Keystone. See this post on the excellent WoW Dig Site resource for more info.
Archaeology is a new secondary Profession (like Cooking and Fishing) implemented in, and requiring, the Cataclysm Expansion. The aim is to compete a series of Research Projects, studies which give you some insight into long ago stories and lore, and in the process perhaps even create a functional artefact unique to the profession. Generally speaking it's fairly slow to level and provides no more day-to-day benefit than Fishing, but the pay-off if you're lucky can be pretty cool. Achievement chasers will be pleased to know that there is a whole new category just for this Profession.
Learning the Profession
Like all secondary professions Archaeology can be learned at any major city. The best way to find the exact location of a trainer is to ask a guard in a capital city, but here is a full list of trainers with linked maps.
The Archaeology window can be found in via the Professions tab of your Skills window (default hotkey: P). From here you can see the current progress of your Research Projects and access a list of completed projects including lore flavour.
Your primary tool for Archaeology is the Survey action, which guides you to the Fragment Caches within a Dig Site.
Where Do I Dig?
Once you have learnt Archaeology a new feature will appear on your continental maps for Kalimdor and the Eastern Kingdoms - four small trowels per map. These maps are 'Dig Sites', and represent small locations where Fragment Caches are known to exist. Unfortunately, you can't just dig anywhere!
the Southern Barrens and Aszhara
Clicking on the Zone will zoom you to the Zone Map, which will show you a more detailed representation of where you can Dig in that zone.
Kalimdor - Minimum Skill Level = 1 - Night Elf, Troll, Fossil and (infrequently) Dwarven Dig Sites Eastern Kingdoms - Minimum Skill Level = 1 - Dwarven, Troll, Fossil and (infrequently) Night Elf Dig Sites Outland - Minimum Skill Level = 300 - Orcish and Draenei Dig Sites Northrend - Minimum Skill Level = 375 - Vrykul, Nerubian, Night Elf and Troll Dig Sites Uldum - Minimum Skill Level = 450 - Tol'vir Dig Sites (Counts towards the 4 total Kalimdor Dig Sites)
How do I Dig?
Once you've reached a Dig Site you're ready to start Surveying. Each dig site contains three Fragment Caches which only you will see and interact with; no-one can steal your Fragments. Firstly, activate the Survey ability.
A theodolite (tripod with an eyeglass on top) will appear with its' eyeglass pointing in a particular direction and a glowing antenna in one of three colours:-
1. Red - Your Fragment Cache is more than 100 Yards away. The error margin for your eyeglass is huge, almost 90 degrees in either direction. Follow the direction of the eyeglass ~150 yards and then re-Survey.
2. Yellow - Your Fragment Cache is between 100 and 40 yards away. Your eyeglass now points in roughly the right direction, and has an error margin of 20 degrees in either direction. Follow and re-Survey ~70 yards
3. Green - Your Fragment Cache is very close (within 40 yards) and the eyeglass points in the almost exactly the right direction. Re-survey at ~20 yards.
Repeat your Surveying until you've found your Fragment Cache. Using Survey when you're within 10 or so yards of your Cache will unearthed it.
The key to narrowing down the location of your cache quickly is dealing with Red results, and with that in mind here are a few rules of thumb:
1. Start in the middle of the dig site - you'll eliminate a large proportion of the site whatever the result.
2. Red results eliminate the area directly behind the theodolite. Multiple Red results chained together should be thought of as gradually cordoning off an area within which the dig site would be. This is especially important for the largest dig sites, in Tanaris, Unbound Thicket etc.
3. In my experience there are areas where Caches usually aren't, most obviously within walls, under water, impassible cliffs and outside the dig site. Use these obstacles to narrow down your search further.
What do I Get?
From Profession Level 1-75 Fragment Caches contain 2 Fragments and thereafter you gain between 3 and 6 Fragments for the category of Dig Site you're surveying, for example Jaedenar in Felwood will always uncover Night Elf Research Fragments. Dwarven Racial bonus grants you one additional Fragment per Cache. These fragments aren't stored as items in your inventory, but as currency visible in your Research Tab. Fragments are never wasted - if you have too many fragments for a Project they'll be rolled over into your next Project.
Additionally you may also get a Keystone in a Cache like the Highborne Scroll. Hang on to them even if you can't use them right away, they're worth a dozen Fragments in compatible Research Projects. Be careful though, they can be traded and sold to vendors.
Research and Keystones
Nine different research categories are currently available: Troll, Night Elf, Dwarf, Orc, Draenai, Fossil, Vrykul, Nerubian and Tol'vir. (Yes, there's a 10th icon... no, I don't know what it does yet).
When you collect a Fragment it's attributed to the Research Project for a corresponding category. Don't worry, there's no fiddling with backpacks required, they're counted as a currency for storage purposes and it's all done automatically. Once you have collected the required number of fragments for that Project you may choose to 'Solve' it, creating the item associated with the project. These items can be kept, or sold on to generate a small amount of cash.
Some projects can be solved more quickly via the use of Keystones. These projects have a number of hexagonal slots below the progression bar within which you can place a Keystone just before you click to solve. Each Keystone boosts your progression by 12 fragments, more than the value of a whole dig site. If you have the opportunity to use a Keystone to solve a project you should always take full advantage of it, there's no reason not to.
The second is greyed out until you've placed a Keystone in the first slot.
Most Projects create 'Common' (Grey) items which can be safely vendored. Details of the Artefact including additional flavour text are stored in your 'Completed Projects' tab.
Sometimes these common artefacts are linked in common a narrative, and uncovering all these artefacts will net you an Achievement. One such story is 'The Tragedy in Three Acts', the tale of Pyramond and Theleste.
Rare Project Artefacts
A few Research Projects are 'Rare', and instead of resulting in a Common item have Rare or Epic rewards. Rare projects typically required substantially more Fragments to complete, but also often have multiple Keystone slots to ease the project along.
There's no way to predict when a Rare project will become available, though the rare projects available to you may depend on you Archaeology skill. For reference, I gained the Fossillized Hatchling project at approx. skill level 150 and Queen Aszhara's Dressing Gown project at 250. If you're after a particular Rare item, such as the upgraded Zin'rokh, Destroyer of Worlds, tailor your continent to that Category (in this case, Eastern Kingdoms for Troll Ruins).
Completing a Survey and looting Fragments can generate skill points in Archaeology up to 100, though 95+ tends to be very infrequent. Solving a Research Project grants 5 skill points. Fragments are never wasted, and so those seeking to maximise the speed of levelling should not solve Projects until they've reached 100.
Rare Projects are generally poor for levelling the skill, though the item you'd gain may be worthwhile. If you're seeking to maximise levelling speed avoid continents heavy in your Rare Projects' Category.
Alternatively, those seeking to level the skill as their character levels should be aware that looting fragments generates a non-trivial amount of XP (modified by the Rested bonus). Level 80 characters seeking to power-level the Profession will gain enough XP to at least level to 83, and normal Alt levelling progression may be significantly affected by the amount of XP you gain. Two gathering professions and Archaeology could easily grant you enough XP to out-level zones you were planning to experience.
You can level all the way up to 525 on one continent if you so desire. Just like Fishing, the location Surveyed or Project completed has no bearing on skill point gain.
Fast Mounts are well worth their gold. Travelling between dig sites and survey points are the most significant uses of time when levelling, and mounts allow you to traverse between dig sites and survey points at speed. At low levels your Archaeology progression will be stymied significantly by a lack of fast mount and flying.
You may rarely come across a Survey where your Cache is inaccessible, either through being in the middle of an obstacle or outside the bounds of the dig site. When this happens, move on to another Dig Site and gain your fragments from that location and then return to the bugged Site. Depleting a dig site re-sets the position of Caches in all Sites, so with any luck that bugged Cache will have moved to an accessible location.