Someone out there went through and compiled all of the free tracks available on the SXSW website and put them in to a couple of torrents you can download. With over 1,000 total songs it won't be the fastest download ever, but once you do get these torrents downloaded you can just throw all of the songs into a folder and then freely browse through many of the artists performing at SXSW.
This could be an easy way to discover a new band to add to your schedule for the festival, like Here We Go Magic for instance. Happy listening.
Photo thanks: Steve Hopson