Three of my favorites:
"Telegraph Road", Dire Straits, from "Love Over Gold" (The studio version is longer and I think better than the live version from Alchemy, mentioned previously)
"Flame Sky", by Devadip Carlos Santana, from "Welcome" (Mahavishnu John McLaughlin also plays on this album. How can you go wrong?)
And another that I can't believe hasn't been mentioned yet...
"The Medley" (i.e. "You Never Give Me Your Money" followed by "Sun King" followed by "Mean Mr Mustard" followed by "Polythene Pam" followed "She Came In Through The Bathroom Window" followed by "Golden Slumbers" followed by "Carry That Weight" followed by "The End" - this continuous piece clocks in at around 16 minutes), by The Beatles, from "Abbey Road".
Chad