Best Live Album Ever...

Off the top of my head...

The Kinks "One For The Road"
Miles Davis "Friday & Saturday Night At The Blackhawk" (Mosaic Records)
Art Pepper "Live At Ronnie Scott's" (Pure Pleasure)
Nirvana "Unplugged"
Stanley Turrentine "Live At Minton's Vol. 2" (Music Matters)
Cecil Taylor "Live In Bologna"

judy at carnegie
bowie: live at santa monica
dead: live dead (or better still: dix pix vol 2: 2/13-14/70, alt: rockin the rhein)
JGB: bay area 78
phish: colorado 88
allmans: fillmore east
sinatra and sextet in paris
neil young: massey hall
and led zep: how the west was won

Sinatra--the Studio Album

A lot of good ones mentioned. I'll add Poco's Deliverin'.

Robin Trower "Live"
Gentle Giant "Playing the Fool"
ditto on Little Feat "Columbus"
ditto Santana "Lotus"
where-as I love YES, generally, "YESSONGS" has to be one of the worst sounding live albums of all time... sounds like a 4-track cassette with bad tape and lots of limiting. Having said that, Steve Howe's performance on "Yours is no Disgrace" and the electric version of "Roundabout" are rip-roaring make-me-feel-18-again performances.
Hey how about Bob Marley's "Babylon by Bus" UK pressing with BIG bust a gut bass.