UPDATED: June 2013
I decided to collect my own short list of hotfixes for that I have recommended for an Exchange 2010/Windows 2008 R2 environment. NOTE: This does not include security hotfixes (WSUS) and is NOT an official list of hotfixes or build recommendation - this is my list of hotfixes that I have recommended for newly deployed Exchange environments as a means to prevent known issues from occurring.
Exchange 2010 Hotfixes Exchange 2010 Service Pack 3 – http://support.microsoft.com/kb/2808208 KB2803727 Update Rollup1 for Exchange Server 2010 Service Pack 3 - http://support.microsoft.com/kb/2803727
Office 2010 Hotfixes Office 2010 Service Pack 1 - http://support.microsoft.com/kb/2460049 KB2597090 Description of the Outlook 2010 update: February 2013 - http://support.microsoft.com/kb/2597090 KB2553391 Description of the Outlook 2010 hotfix package: December 11, 2012 - http://support.microsoft.com/kb/2553391 KB2832226 Office 2010 cumulative update for April 2013 - http://support.microsoft.com/kb/2832226
Office 2013 Hotfixes KB2738013 Description of the Outlook 2013 Update: April 2013 - http://support.microsoft.com/kb/2738013
Base Windows 2008 R2 SP1 Hotfix KB 2775511 – An Enterprise Hotfix rollup for Windows Server 208 R2 SP1 – http://support.microsoft.com/kb/2775511
Windows 2008 R2 Post-SP1 Hotfixes KB2754704 http://support.microsoft.com/kb/2754704 -- MPIO KB2471472 http://support.microsoft.com/kb/2471472 -- NDIS KB2769369 http://support.microsoft.com/kb/2769369 -- WIN32SPL KB2494016 http://support.microsoft.com/kb/2494016 -- CSVFILTER KB2578113 http://support.microsoft.com/kb/2578113 -- CLUSRES KB2614892 http://support.microsoft.com/kb/2614892 -- MOUNTMGR KB2536275 http://support.microsoft.com/kb/2536275 -- SYS KB2619234 http://support.microsoft.com/kb/2619234 -- RPCHTTP KB2724197 http://support.microsoft.com/kb/2724197 -- Kernel KB2779069 http://support.microsoft.com/kb/2779069 -- CLUSSVC KB2699780 http://support.microsoft.com/kb/2699780 -- Registry * Updated from previous hotfix notification release
Lync Server 2010 Hotfixes Updates Resource Center for Lync - http://technet.microsoft.com/en-us/lync/gg131945
NOTE: If you cannot download the hotfix from the KB, then first, determine if you really need that hotfix and if so, consider contacting MSFT support for that build or look for another, related hotfix with similar files and build.
Have Fun... Doug