I would like to install Filemerge, but can't find where to go to download it. Where can I download it?
FileMerge is part of Xcode 4.x by Apple which you can download from the Mac App Store.
The following is taken from the description:
But FileMerge.app is now embedded inside the Xcode.app package and is not easily accessible as a standalone tool... Unless you do this:
Now you can use as a standalone tool, as before!
Alternatively, if you don't need the entire Xcode distribution, DiffMerge is also very similar and free.