I don't know if this is common knowledge but hopefully some people here will be interested to know that around 17,000 live recordings from the "sugarmegs" collection were recently posted on archive.org. I think there'll be something for everyone, but you'll need to check for yourselves as I can never remember the names of many performers younger than about sixty.
A quick search turned up hundreds of concerts by Bob Dylan and Neil Young, around eighty Joni Mitchell (1965! to 2000), nearly forty Leo Kottke, and a fair heap of Miles Davis and John Coltrane. A lot of other names I tried turned up at least two or three tapes. Apparently a few thousand more titles are due to be added in October.
The only bad news is that the bitrate is fairly low (40kps), which of course is sacrilege to some tapers, but most people should find them perfectly listenable.