According to this website, Lisa Kudrow (of Friends fame) is slated to star in the Grey's Anatomy spin-off. This hasn't been reported anywhere else, and may just be a rumor. All the article says is that she is supposed to star alongside Kate Walsh in the new series. More information as it comes in.

UPDATE [03/16/07]: According to Mike Ausiello at TVGuide.com, Kudrow is not joining the cast:

Lisa Kudrow is not — let me repeat, not — joining the cast of Grey's 2.0. As one ABC source flatly puts it, "All of the roles have been cast."