Since a link to BPL's first site was in the original guiding post on this subject, let me lead you to the first archived page of my first library - Denver Public Library from Jan 27, 2003. Um, the graphics really don't work... oh well. Looks a bit like one of my earliest sites: Myogen.com from August 16, 2000.
One of my favorite things to do with the live music archive is to look up concerts on a friend's birthday (I often just start with the link for finding shows on today's date and then change some text in the address bar to get the date I want) . I can usually find something significant - I found a cool Dead show in Telluride performed on my wife's 16th birthday for example (at the time you could download a lot more Dead content). Then I download the show and make a set of CDs as a gift. Another cool date to check - new year's eve. I have great shows of Yonder Mountain String Band in 1999 and then in 2000. One word of caution - diving into this archive can consume MASSIVE ammounts of your time. You'll also come across major audiophiles who are very anti-MP3 and other lossless compression formats. Read up on ogg vorbis and flac to really enjoy your time here!