I'm guessing most people remember their first "run" in with homestarrunner, and though I found the stuff infectious for a long time, I really haven't checked back for a while. I guess I can't call web animation nostalgic, but a relatively new episode of Teen Girl Squad reminded me of the absurdity and hilarity of the shorts.
If you haven't been back there in a while, take a look and remember the glory of Trogdor, Fluffy Puff Marshmallows, and Strong Bad Email. If you've never gone there, Trogdor will burn your thatched-roof cottage.
Apologies for the less-than-stellar quality of the embed, but HSR.com has yet to provide an easy embed option.