It's back up. From the site: "If you've arrived here from yardoc.org/docs or rdoc.info, don't be alarmed. We've finally merged the two sites just like we said we'd do, And we made sure none of your project URLs were harmed."

Excellent! I think one of the biggest wins of rails 3 is the partial undoing of fragmentation that the community was going through. Wins all over the place.