My favorite download sites are.
1. Archive.org's Live Music Archive.http://www.archive.org/details/etree
It's a curated site that only allows recordings to be posted if it matches the band's taping and trading policies.
2. bt.etree.org is a bittorrent site for recordings that also follow band taping and trading policies.
is where I go when I want a official band release of a show I attended.
These three sites have lossless files in FLAC or Shorten as well as mp3s.
4. If don't want a whole CD, I'll buy a track in mp3 format from Amazon.com's store.