Spamalot and Avenue Q are at the top of my favorites soundtrack-wise (I have sadly never seen them for myself). On the ones I have seen, I love The Producers, The Phantom of the Opera, A Funny Thing Happened on the Way to the Fourm, and The Lion King.
As for Off-Broadway stuff or the ones I want to see...I won't bore you with a long list.
I also loved the production of Capitol Steps that came here last sunday, although I'm not sure if that really counts as "Broadway" or even a play. It changes very frequently to keep up with current events.