Does anybody know any good penetration testing tools for SharePoint?
There is a web application (in addition to network and client side) penetration testing tool called Core IMPACT that has exploits specifically for Sharepoint. It has been developed and updated by Core Security Technologies.
Check the answer to similar question here : http://social.msdn.microsoft.com/Forums/is/sharepoint2010general/thread/cfdbf4e7-83d2-43b9-9aaa-6379cbad1cb0
You can also find some more tools here.
There's quite a few resources on this blog posting. Specifically there's a link to Stach & Liu's page here which has some tools and presentations on sharepoint testing and security.