[hlidotbe]

We use Redmine here (~4 people) and it's great. Rails backed, lots of plugin if you need more and easily extendable.

It integrate cleanly with CVS, Git, Mercurial, SVN, ... and we'll even do invoicing with it in a few weeks.

There are paid hosting options if you don't want to maintain it yourself.

[Zeleb0ba]

Can you shed some light on Redmine's invoicing? I have not seen any plugins that give that functionality.

[hlidotbe]

We use this one: http://github.com/edavis10/redmine-invoice-plugin. Simple (a bit too simple) but gets the job done and can autofill based on timesheet entries.