Man, I love Tull...
Everyone's heard Aqualung a zillion times, and locomotive breath is posted, so... here's My God -- powerful song.
P.S.
I had them all, Songs From the Wood, Broadsword and the Beast, Aqualung, Passion Play, Living in the Past (great song as well as album, BTW) Thick as a Brick, Too Old to Rock and Roll Too Young to Die, etc. etc.
Gateway music for punk rock, this and Black Sabbath, I always thought. I never met any punk rockers not into Jethro Tull and Ozzy. You have this quiet little melodic rebellion music and it inspires a whole generation of spiky anti-Thatcherite Brits and anracho-punk. It doesn't seem that way, but think of early Damned or even the Pistols. Sure they borrowed from the Ramones who borrowed from the garage rockers and the R&B/do-wop bands, but the connections are there.
You can hear Black Sabbath influences in like pretty much everything and a lot of Tull in a god bit of stuff too (Crass, maybe even a little Subhumans, anyone?)
And in that vein: Hymn 43