Microsoft released a guidance document for branching and merging using Team Foundation Server. This extensive guide explains about various branching and merging patterns and how to implement those patterns using TFS. It also has information on how branching/merging is implemented in Microsoft product teams. Check out the following community page for more details,
http://www.codeplex.com/BranchingGuidance/Wiki/View.aspx?title=html&referringTitle=Home
I also came across a tool “Team Foundation Side Kicks” which is really useful for merging. Though most of the features provided by this tool are available through TFS command line utilities, this tool UI is very good. Check it out at following site,
http://www.attrice.info/cm/tfs/index.htm
It also has so many additional features other than merging.