For Mac users who need to run the occasional Windows app, you’ve got a couple of options now. Wine has long been available for Linux users to run some Windows apps on top of a Windows API compatibility layer – CodeWeavers have taken this and produced a commerical version called CrossOver, and CrossOver Mac for Mac OS X, which offers support for running Windows MS Office plus some other apps. It’s not shipping yet, but when it does it will be priced at $59.95 which is a good price if you desperately need MS Office on your Mac.
The other options offer fuller support since they allow you to run Windows directly on your Mac – BootCamp from Apple allows you to dual boot your Intel based Mac to either Mac OS X or XP. The other option which is interesting is Parallels, which is Vitualization software (like VMWare) and allows you to install and run XP as a guest OS ontop of a currently running Intel-based Mac OS X machine.
Reghardware.co.uk have a lengthy article covering both BootCamp and Parallels, and is worth a read if you’re considering these options.