I saw the demo of parallels and I really think it's a good option.
Andy, Parallels can run Linux now but I'm not sure if it's possible to run several OS at the same time. However, I will use only Windows for some specific applications. I really love the possibility to drag and drop files between both desktops and others features:
Run Windows programs like native Mac applications with Parallels Coherence, now with Apple Expose’ and transparent windows support
New! Open Windows files with Mac apps and Mac files with Windows apps
using Parallels SmartSelect
Share files and folders between Windows and Mac OS X
New! Access Windows folders and files without launching Windows
using Parallels Explorer
New! Run selected PC-only 3D games and graphics applications on your Mac
New! Map Mac folders to Windows letter drives for quick and easy access to your favorite Mac files
New! Keep your favorite files at your fingertips. Windows now mirrors the contents of your Mac’s Home Directory.
Parallels Transporter lets you to migrate your entire existing Windows or Linux PC system to your Mac in just a few simple steps. Now you can even use FireWire!
The price is the same for VMware: $80
Maybe VMware have all these features now. I used it 3 years ago...