So I am relatively new to using merge tools. I have been developing with them for about a year. Merge tools become a necessity if you are developing in a team, or working on branches in your source control system. You do have to be ultra careful when you are merging against another developers changes. The merge tool you use for this is key, a good tool will help you quickly assess the differences and let you combine them quickly and accurately.

Tools that cost $$$

At work we use Araxis Merge and it is a great tool, it is a very polished piece of software it makes merging files easy, it supports three way merges and has a fast folder comparison utility. It is relatively expensive at $79 but represents good value for money.

Jeff Attwood wrote an article on his blog about Beyond Compare, I am going to try this out as I need a tool for my dev work at home and this is only $30 according to Jeff it is every bit as good as Araxis and a lot cheaper.

Tools that are free

Scott Hansleman has written about free Diff Tools on his blog his pick of the bunch is WinMerge some of the others he mentions are KDiff3 and  DiffMerge .