BuddyPress.org

Actually I disagree. I would suggest looking at Kaltura for video, and I think there is another media plugin that handles video and images although I haven’t experimented with either, I think that BP-albums is being updated to handle other types of media. If you can wait there is a very interesting plugin being developed as a Google Summer of Code project that will turn a WordPress / Buddypress install into an LMS, it has some interesting features and looks to be very extendable. I expect it will be like Buddypress itself and spawn a series of additional plugins that enhance its features. Have a look at it at:
http://sushkov.wordpress.com/

Existing LMS systems do have a lot of pluses, but many are either difficult to customize and quite rigid (Moodle comes to mind) or very difficult to install and configure (Sakai project for example). That said, it may be easier to get a quick system up and running and your intended audience should reflect your choice of system as well. I find that most systems are aimed at older students (high school or university and beyond) and so do not fit what I hope to do with a learning system.

Hope this helps a little. All the best.