I found this link on another board, but I'm sure we could get plenty of use out of them too.
Graphic-intensive linky.
A little excerpt:
I'm out - abandoning or withdrawing from a situation or conversation out of disagreement, disinterest, or distress
O RLY? - used to convey a deadpan response to something doubtful, dumb, or unimpressive
This oughta be good - conveys excitement over a brewing internet fight, of which one chooses to not participate, but merely enjoy as an audience
Jack Donovan, b. Christmas Eve, 2009.


Re: A comprehensive glossary of gifs
LOVE!
Total newb question-
How do you insert a gif into a post?
applause.gif
I don't know either but it says to right click and copy the image code. I'm on a Mac and the only option I have to copy image address. So here I am testing it.
I usually get my gifs from photobucket or tinypic so then I just use the IMG code they provide.
ETA: copying image address does not work.
some of my faves are on there! I love it!