Eye On Springfield is a retrospective of Simpsons hilarity spanning from seasons 1 to 9, when it was still funny.
I would disagree with the "still funny" bit; there are plenty of classic episodes in seasons 10 through about 18, though the most recent seasons have definitely fallen off. Site posts range from scenes in an episode, sometimes with an accompanying quote, to sound clips. It's a great site, and I highly recommend it for a laugh.
I'm also glad to see that I'm not the only one who, in the words of Patrick Cassels, has:
that annoying habit of beginning half my sentences with, "Remember that Simpsons episode where..."