There are lots of projects that enable groups to organize themselves, gather ideas and organize documents.

Does anyone know any Free Software solution that is somewhat tailored to the needs of an action group? It should be easy to use, enable and invite people to participate and provide some means of collecting signatures for the cause. Ideally it’d also provide a Wiki for later, a contact forum and some means to organize and collaborate on ideas, brainstorming and schedule meetings.

I’d also like to hear about other solutions, even if they target something broader and I’d have to customize them. Or miss some features but I can combine them with other software. Most importantly it has to be easy to use and inviting, so people would like to participate.