I recently had to provide our infrastructure and security team information regarding SharePoint 2010 service accounts, required permissions, database roles and permissions, registry and file system permissions needed etc. I compiled all the info into an Excel workbook similar to what we use to have in SharePoint 2007. If you are interested you can find the document here http://code.msdn.microsoft.com/sp2010security/Release/ProjectReleases.aspx?ReleaseId=5245

I plan to keep this document updated, if you have any comment or u find missing information or something is not stated correctly please email me and I will update the worksheet