dvd_commentary is hosting the 2008 Multifandom DVD Commentary Challenge. Info is here, but basically you pick one of the participating writers (or ask someone yourself if they're not on the list) and do a DVD-style commentary on one of their stories. You must have the writer's permission to do a commentary on one of their fics, but you can do as many as you want.
There's no deadline for signing up. The deadline for posting commentaries is 1 October 2008.
Author Permission Sign-Ups
Story Claim Sign-Ups
Note that more than one person can do a commentary on the same story, so claiming a story is just a matter of saying, "Yeah, I plan to do this."