Hey, Inertia, after reading dateopia and Terry Van Horne's answers, I think you might want to peek at this site. It's not been around that long, but it's definitely attracting an audience since it fills a niche and has the right features.
Fiddle Hangout - Welcome to the Fiddle Hangout!
The same folks designed this one also--
Banjo Hangout - free banjo lessons, tabs, discussion forums, links, banjo players directory, banjo reviews
Each of these sites allows members to blog, post videos, post (no copyright problem) sound clips, classified ads with payment on the honor system when the item is sold, product reviews, and there's a fairly active forum. I may have missed a feature or two. So yeah, this might be a way to go, if you can find a music niche that will work and that interests you.
This site is also starting to get some attention:
MusicMoose.org - Home
They use youtube and other video sites to bring people into the site for their pretty good lesson videos. (Jeff Wisor, one of the fiddle teachers, plays with David Bromberg, and Sue Cunningham cleans up at many of the major Fiddle Contests, and that is key to this site doing well. I'm sure that the teachers on other instruments are also notable.)