Share your favorite subreddits

Over in the Digg acquisition thread, there's a fair amount of talk about Reddit, and one comment thread ended up with a bunch of folks posting the subreddits that they thought made reddit great.

One thing that's always been lacking on reddit is subreddit discovery...

So, in the spirit of sharing greatness, why not share your favorite subreddits?

Some of my more esoteric/fun favorites:

/r/mildlyinteresting/ /r/BuyItForLife/ /r/PostCollapse/