Stumbled across a nice SQL Server build number site a while back that has a comprehensive (I think?) list of every SQL Server build from the SQL 7 beta 3 up through SQL 2012 RC1 including every CU and hotfix along the way. There is also a link to download the KB that corresponds to each build if appropriate. If you happen to know of a build that isn’t listed, it looks like this site is somewhat crowd-sourced, so post the details in the comments and it will likely make it up to the main page.
(If you look in the comments, you can even find little “anonymous” nuggets, such as the following: “SQL2012 RTM is 11.0.2100.19”)