Scheduling meetings: meet-o-matic.
Shared online calendars: online calendars
Mailing lists: mailing lists to help a community email each other.
Use an online room booking facility.
Send instant messages to one or more people using an instant messaging tool.
Talk to one or more people at low cost using internet telephones.
Alert people to aspects of your project using online news feeds
Share diary-like updates about your work online using a blogging service.
Collaborate in the management of project tasks using the online project management software such as dot project
Try using wikis to easily collaborate in creating web pages.