This site now has a very handy feature built into called "Organic Groups". A group can be started by anyone, for free, and is essentially its own website within theicarusproject.net. Each group gets its own:

Homepage

The URL will usually be in the format of "theicarusproject.net/mygroupname". Just like the main icarus homepage, this is a blog. Unlike the icarus project homepage, however, any member of your group may post to it, and when they do an email of the post will be sent out to all group subscribers who wish to receive them, along with any future comments on the post.

Wiki

This is just like a regular wiki - any group member may post to it, then any group member may edit it. It tracks revisions so if someone messes it up it can be reverted to a previous state by any group member.

Calendar

Your own group calendar. You can easily add regularly occurring events, like a biweekly group meeting, or special events like a group fundraiser. Emails are sent out to group members for special events but not for regularly occurring event.

Image Gallery

Your own group image gallery!

Contact Page

This is a form that anyone with an account on the site can use to send the group manager (the author of the group) an email.

Task List

A collaborative checklist of things that need to get done. Very user-friendly, completely custom built. Only visible to members of the group.

Contact Database

This allows your group to store email addresses, phone numbers, mailing addresses and names in one searchable, filterable table. Obviously, these are only visible to group members.