What's a good Mac equivalent of WinMerge? WinMerge is an excellent and very powerful file merging tool, but as the name would imply, it's Windows only.  What's a good equivalent on the Mac?
You can use FileMerge, Apple's diff solution. It's free and it comes with every Mac OS X install.
The only downside is that you have to install the Developer Tools. You can find them on your DVD install that came when you bought your Mac (Snow Leopard or earlier). You can also get the developer tools from the App Store if your version of the OS supports that.

Then, you can find it at /Developer/Applications/Utilities/FileMerge.app