(3) Google Groups: Maybe this isn't universal, but we've had a hard time maintaining email lists on the university servers. Google Groups gives you an easy way to start and manage email lists without going through university bureaucracy. A typical problem with email lists is that one wants to include people without keeping names and addresses that are no longer valid or relevant. With Google Groups the admin is easy and can be shared between the researchers leading the project, seminar or reading group. You can also share documents through the Groups.
Hopefully, this is just the start. Soon we'll use Google Wave for collaborative research, integrating the above features in one interface.