Best Free Source Code Compare Tools

Not only computer programmers need a source coders compare tool, but also for any document writer, many people need a nice compare tool. Here I give several nice tools which I have ever used:

1: SourceGear's DiffMerge:

Free and Open Source tool, I prefer to use it .

2: WinMerge:

Nice one too and free, and also you can get a portable edition

3: Beyond Compare:

Much more professional, before I knew WinMerge and DiffMerge, I used it. But it is not free.