You can find out information on Parallels here. I've got to say that I have been running Parallels on my MacBook Pro since I first bought the computer (over 2 years ago) and with the most recent versions (both OSX (Lion) and Parallels 7) I am somewhat dissatisfied with the current performance. It used to be very good prior to the Parallels upgrade.
You should also be aware that your OSX comes with "BootStrap" which will (although you can't run both at the same time) will turn your Mac into a PC. There is sharing across the two systems but you can't run both at the same time. The advantage there, is that is Apple software built into the OS.