A number of classic episodes from seasons 1, 10, and 20 are available on iTunes now. I think they're under a heading called "Sesame Street Classics: Volume 1". I haven't downloaded any yet (I have quite a few things to do today), but browsing through it includes Telly's debut appearance, a season 20 epsiode where Elmo meets a deaf friend of Bob's (I've seen a page on Muppet Wiki about it), and a number of episodes that appear on the Old School releases (episodes 1 and 1186). The way the episodes are titled is interesting. One of the first season episodes is listed as "An Orange Oscar and a Green Grover". Another has some title relating to Grover being a waiter.