http://sourcegear.com/diffmerge/index.html

Product Features

  • Diff. Graphically shows the changes between two files. Includes intra-line highlighting and full support for editing.
  • Merge. Graphically shows the changes between 3 files. Allows automatic merging (when safe to do so) and full control over editing the resulting file.
  • Folder Diff. Performs a side-by-side comparison of 2 folders, showing which files are only present in one file or the other, as well as file pairs which are identical or different.
  • Configurable. Rulesets and options provide for customized appearance and behavior.
  • International. Compatible with 42 different character encodings.
  • Cross-platform. Identical feature set on Windows, Mac OS X, and Unix.

I have to tell ya, this will probably be the last diff/merge tool you'll ever need.