A player going by Antiarc has written a few tools that pull data from the Armory on every character in your guild, and then give you some great tables you can sort in various ways. For instance, I can look at the character stats page and gloat over the fact that I'm the highest Spirit and +healing Priest in my guild, and then look over in the spec column and realize that's because all the other Priests are Shadow (besides one level 64). Or if I'm looking to get something crafted, I could call up the profession comparison page, and see who's put in the effort to get a Jewelcrafter up there. Finally, if I'm looking to see who can join me in some thrilling Heroics, or just who's got way too much time on their hands, I can check their standing with the various factions.
Due to the fact that these scripts do pull down and process quite a bit of data, they take a while to run; but the results pages are static, so once you've generated your results you can share the link around and it'll load quickly. If you just want to see what the pages look like, please do use the preview pages to avoid undue server stress.
By the way, if Antiarc's site goes down or just to spread the load around, there's a mirror here. Now go forth and compare!
[thanks, jbob, for sending this one in!]