Sharepoint 2012

http://www.sharepointpromag.com/article/migration/migrating-to-sharepoint-2010

http://social.technet.microsoft.com/wiki/contents/articles/8666.sharepoint-2010-best-practices-en-us.aspx – this link  is very useful for all migration troubleshooting, procedures, etc

http://technet.microsoft.com/en-us/library/cc263447.aspx

http://solutionarchitects.org/articles/2011/04/06/migrating-code-from-moss-2007-to-sharepoint-2010.htm

http://rcpmag.com/articles/2010/07/01/migration-madness.aspx

http://info.axceler.com/Blog/bid/51255/Understand-Your-SharePoint-Customizations-Before-Migrating