There's Lambda the Ultimate (lambda-the-ultimate.org). That's not so much for experiments in programming as it is for PL theory discussion - fairly heavy on the academics, but very good.
Oh yeah, Lambda the Ultimate. I've read a few threads there, and I should probably check it out more often, since I can learn a lot very quickly that way.
But yeah, it's not a place programmers come to talk about random general-purpose snippets of code they've made, the way this is. I'm sure there are lots of sites like that too, but I guess I like the balance between that and PL design which this community seems to pursue. ^^
