Ustream.tv (description)

Ustream.tv is a site that allows you to put on internet concerts. If you have a web camera and a microphone, you could play concerts to as many people as want to watch. Treat your online concerts like in-person concerts, with mailings, a show schedule, and similar promotion.

There are a number of very good tools on this site, however the sound will only be as good as your mics and setup. You should test the sound carefully, and if you can, use a miniature mixing board and true XLR mics rather than the ones in a laptop. Also, if you can get a real video camrea that has an S-Video connector, you will get better quality results. Lighting, sound, and camerawork matter.

It is possible to have multiple cameras put on your concerts, but you need external software to do this at this time. Multiple cameras with a switchbox can make a big difference, however, since a single camera on a tripod can make for a boring video.