It seems like most of the mixoffs so far are getting good participation, which is great!
If you want to get some more participants, and help grow our site here, you can do something like I did.
Visit one or two other forums that you regularly post on, and start your mix off there, too. Link to your post here for the files and info, but suggest that people can post mixes and comment on that forum as well. You don't want to spam the forum, just to share your mixoff with a larger audience.
If people just want to participate on the other forum, that's fine. But hopefully, they'll see what we have going on here, and join us.
Here's an example of the idea:http://studio-central.com/phpbb/viewtopic.php?f=119&t=79495
Again, don't go crazy, and make it clear that people don't have to join mixoff.org to participate.
You can, of course, email friends, link on facebook, etc, as well!