Here are some handy tips for the Windows command line:

• 'Findstr' is 'grep' for Windows. I don't know when they slipped this in, but I missed it for a long time.
• Use 'setlocal' and 'endlocal' in batch scripts to limit the scope of changes to environment variables such as PATH.
• 'Pushd' works just like 'cd' but saves your current path on a stack. Calling 'popd' will change your current directory to the path on top of the stack. These are godsends for navigating deep path hierarchies.

Let me know if you have any other tips and I'll add them to the list.