E-mail is the basis of many collaborative efforts. There are two free web-based services that allow you to easily set up e-mail groups; eGroups and SmartGroups. SmartGroups provides some additional services that are helpful for a group effort. These services include a group calendar, voting system and document area. With SmartGroups you can also keep up with all your latest group news by using a WAP enabled mobile phone. You can even send an email to the whole group from you phone. If you are into rolling your own services, Mailman is an excellent Open Source mailing list manager with very nice web integration.