Windows Server 2008 Security Events Posted
Fadi, Ned and Brian of the auditing team have documented all the auditing events by audit policy category and subcategory for your reference.
Check it out in the Knowledge Base.
Even better, they documented all the events in spreadsheet format, and that's propagating to the Microsoft Download Center. I'll publish the link when it's online.
2008-04-17 UPDATE: Brian just sent me the link: here is the spreadsheet.
2010-04-01 UPDATE: Here is the link to the updated spreadsheet for Windows 7 and Windows Server 2008 R2.