If you plan to continue with the other adventures, T1 is best leading into the Temple of Elemental Evil. That's a campaign unto itself. U1 is pretty good too if you detail out Saltmarsh, using it as a base of operations, then moving into U2 and U3. B3, B4, and N1 are good adventures, but they are self contained, preventing much adventure beyond themselves. I honestly don't remember B5, so no opinion on it.
Some other options to consider would be B1-9 In Search of Adventure, which is a mega-adventure that takes some of the best from B1-B9 (duh). It gives the party a home base and several adventure hooks (several of which lead into others), but it's done in a way that the players have to choose which adventures to pursue, because due to time and other adventurers, they can't all be done.
A good adventure for building off of, similar to B2 is The Secret of Bone Hill (L1). Not only does it provide several adventure points that can be expanded upon, but there are also followup adventures in L2 and L3.