Tortoise are an excellent Chicago-based post-rock band. I have recently purchased the excellent value Lazararus Taxon, a 3 CD 1 DVD box set for £13! This set from you Tube is on the DVD:
The highlight of the DVD is the band playing with three drummers at a Jazz Fest - awesome!
Also on You Tube are:
A 30 min live set
Four-day interval video
Clip from ICA the Show