Check out this great live version of Aqualung I found on YouTube. Man, I never actually saw any video footage of the band before and I can't believe what a clown Ian Anderson is - and I mean that in a good way. He's really a great showman and while I'm sure many are easily turned off by his antics, I think it's a lot of fun. As for the song, this version is very good but it's pretty hard to beat the studio version, if you ask me.
Incidentally, what are people's opinions of Jethro Tull on this board?
I personally much prefer Tull to Gabriel era Genesis simply because their music connects with me more. Actually prog is not a genre I'm overly fond of but Tull were more than merely a prog band with their great mix of rock, folk and blues (with a bit of jazz and classical thrown in too).