Technically not a band.
Robert Plant and Jimmy Page Unplugged ('Unledded'). I got this for Christmas and have listened to it a few times, more so recently and there are some real gems here. The updated versions of 'Kashmir' and 'The Battle of Evermore' in my opinion are far, far superior to the original recordings; for instance the Mandolin in the latter sounds wonderful, it's impossible to describe. There's some really great musicians on this record and the quality of recording is nothing short of phenomenal. The energy is great, the arrangements are great and the experiments nearly all pay off. I'm not a big Zeppelin fan, but I really like this. Check it out if you get a chance.
For instance: http://www.youtube.com/watch?v=TfE9KhuhsxI