SHAREPOINT ONLINE CODE ANALYSIS FRAMEWORK (MSOCAF)

Here is a new tool from MS to review your SharePoint custom code
https://caf.sharepoint.microsoftonline.com/

SharePoint 2010 Sanbox Resources

Here are the some of the good links for learning SharePoint 2010 Sandbox

http://msdn.microsoft.com/en-us/library/ff798382.aspx
http://msdn.microsoft.com/en-us/magazine/ee335711.aspx
http://msdn.microsoft.com/en-us/library/gg317460.aspx
http://msdn.microsoft.com/en-us/library/ff872402.aspx#InsideSP14_Ch4_UFTP

Also check out these channel9 videos on sandbox
http://channel9.msdn.com/learn/courses/SharePoint2010Developer#SandboxedSolutions

I had issue running sandbox on those dev servers which is not connected to internet, and after multiple reply to this thread I get solution for that

http://social.technet.microsoft.com/Forums/en/sharepoint2010programming/thread/ff3a5e65-dc5b-4b80-b8c9-752adcc3a903