I haven't noticed much, myself; on the other hand, I haven't explored much. There is an 'official fanfiction project' thing on youngwizards.net (http://www.youngwizards.net) (or .com (http://www.youngwizards.com); they're both part of the same site, but they hold different things) in which Diane Duane wrote the first scene for this script, and then fans write each successive scene. Then the best submissions for each next scene get voted on.

What there is, you can find rec'd on youngwizards; there's also a fic challenge thing going on right now at myriadwords.