I'm actually writing this on July 4, so I'm in the mood for a little fun while we're waiting for the dust from patch 4.2 to settle. If you've been around the site before, you've probably seen my worshipful odes to the Dalaran fountain, which I still think was one of the best and most brilliantly eccentric parts of Wrath of the Lich King. (I think archaeology's very similar overall, even if Blizzard's still working out the kinks.) While I took a look at some of the coins almost three years ago during the Wrath beta, it occurred to me recently that we never actually did a guide to them and their importance to WoW's mythology.
So here's the deal: You're in a magic city. The city has a magic fountain. Lots of very important, somewhat important, and unimportant people in the world made wishes and tossed coins into the fountain, and the fountain (being magic) remembered them. Some of the wishes are funny, many of them are sad, many are quite thought-provoking, and a few are simply tongue-in-cheek references to the Warcraft universe (Archimonde's is probably the standout here). If you fish all of them up, you'll get A Penny For Your Thoughts, Silver in the City, and There's Gold in That There Fountain, with the completion of all three granting The Coin Master. So if you're going for the fishing meta Accomplished Angler (ha ha! sucker!), you'll need the coins even if you're not interested in the lore behind them. You monster.
Warning: If you're still playing your way through The Burning Crusade and Wrath content, there are a lot of lore spoilers in here, so be careful.
EDIT: This guide is now finished! You can find the full series here: