Vavavoom

Check this one out. This site contains some interesting statistics including the most covered songs, the most covered artist, the most covering artist and what I think is the most interesting: a chart comparing the years between the cover and the original. If this trend continues, we'll be listening to REO, Molly Hatchett, and the STYX again in no time!
PS: This challenge will be soon followed by others such as greatest songs, classic rock bands, 80's bands, grunge rock, etc. So, if you're on the fence with one of your favorites, you can always use them later.
Here's a couple of sites that offer tons of live music for listening and for downloading. They've got lots to choose from; Bruce Hornsby, Dead, Medeski Martin and Wood, Keller Williams, Allman Bros, Bluegrass, and much much more. Nugs and the Music Archive