Beyond Compare
If you’ve ever tried to troubleshoot code/files (like I’ve been doing for the last several weeks as I tweak my CSS and php), there’s nothing like a handy tool to help you compare those files.
My favorite is a PC-based one called Beyond Compare. It color-codes the differences and allows you to move text from one file to the other. You can download a free trial and it’s only $30 to buy.


For on-the-go comparison, you can also use the quick-n-dirty WinMerge (Portable), which has the advantage of being GNU-licensed, lightweight, and (of course) portable ;-P.