How can I enable my users to create audio and video galleries, where they upload their own content and allow other visitors (members or non members) to be able to play their stuff, just like myspace.com.
i just use creative tabs for this (there's an article here on how to do it if you're unfamiliar). You also have to make sure the wysiwyg editor does not strip code (like most of them)...I use fckeditor for this and it works fine.
Check out User Home Pages 2.1.1 by Ravenswood IT. I'm replacing all of my Media Galleries with it on BandThreadz.com. UHP2 allows each user to upload files to their own directories. It works with image and multi-media files.