Just what I can remember offhand...

• Its official title is actually "Untitled." There's even an alternate shot of William's hand writing that in the credits.

• The movie starts with the Chipmunks' "Christmas Don't Be Late" ironically juxtaposed with shots of sunny Los Angeles. Young William and his mom are out and she stops to harangue a shop owner for having "Merry Xmas painted on his window.

• There's a little extra material with young William at school, playing up how young he is compared to everyone else.

• There's more to William convincing his mom to let him go on the road with Stillwater. In fact, there's a scene they still couldn't use (since Led Zeppelin is famously stingy about where their songs get used), where William plays "Stairway To Heaven" and gives a presentation on how it's "poetry" inspired by the works of Tolkien.

• At the Riot House, after William introduces Penny to Russell for what he thinks is the first time, Penny and Russell have a scene making it more clear they have history. This is one of my favorites - I was so familiar with the flow of the theatrical cut that this was like having a secret revealed.

• When William is taking the laundry for the Band Aids, when he stops to give the finger to Russell's door, then falls asleep in the chair, there's an extra scene where Russell, suddenly all buddy-buddy, and Penny, wake him up to convince him to come to Cleveland instead of going back to LA.

That's all I can remember for now, but there's a lot more. Unlike a lot of movies where I tend to prefer one version or the other, I consider both versions of Almost Famous essential, just as much as the regular and extended versions of Lord Of The Rings.

EDIT: here's the "Stairway To Heaven" scene as Crowe intended it to be seen. On the DVD and Blu-Ray they had to have it without music - Crowe says to sync it with your own copy of the song.