Practical UML
UML Overview
I dunno, it depends on how big team is. Class/Sequence/Use cases is what mostly used for me I think. The most important thing is not overuse diagraming, couse the main goal is to help comunicate among team, help understand things same way, not just to make some useless diagrams papers and not use them.
However very complex system developed by group of teams, obviously require more diagrams I think, just to make sure everyone knows what they are doing and how things relate in system. There's quite lot good tools these days that help in modeling.
