My last company used <a href="http://twiki.org/" rel="nofollow">http://twiki.org/</a> but we got tired of their security track record <a href="http://twiki.org/cgi-bin/view/Codev/TWikiSecurityAlerts" rel="nofollow">http://twiki.org/cgi-bin/view/Codev/TWikiSecurityAlerts</a>