Start with newsgroups. Cop a decent newsreader (95% of them are free) and subscribe to blues, bootleg, 1990's rock, etc. Also this search engine IS indispensable!!
http://www.binsearch.info/browse.php?bg=alt.binaries.sounds.mp3.bootlegs

Request shows. Mule people are very free with their posts. When they come again (Right now it's very thin) they'll hit you with 3-4 concerts, usually no throw aways in the bunch. You could go bit torrent but it's a "major hassle." GET the newsreader and all will open up to you. Bootleg (there's two major's) are worth checking 2-3 times a week. And Yes, Warren Haynes Is God. *Soft Smile*

Hello Liz, Any special shows you are looking for? I have a buddy livin' in Whistler who has a large selection of Mule,Dead,SSMB and other bands live performances.
JB