Best free collaboration tool now that Google Wave is no more? [closed]

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Closed 8 years ago.

With the unfortunate demise of Google Wave what is the best alternative free project collaboration tool that you use for your side projects and non-funded software start-ups?

Answer 1

So far this is my first choice:

http://www.teamlab.com/

Answer 2

Sign up with Runby, which integrates a Google Wave approach (hosted conversation) with email:

http://runby.me