OS X: Parallels Desktop is our favorite tool for running Windows on your Mac, and right now you can grab Parallels Desktop 7 for only $10.
Parallels Desktop is usually $80 for a new license, and while Parallels 8 is the newest version available, version 7 is still a solid program. Not only can you run a Windows, Linux, or OS X desktop on your Mac, but you can run Windows applications on your Mac desktop as if they were OS X applications, which is a killer feature. Newegg's currently selling version 7 for $29 with a $20 mail-in rebate, bringing the total price down to $10—not bad, even for an older version of the software. Check out what's missing in version 7 compared to version 8 here to see if it's worth the discount, then head over to Newegg to buy a copy. The rebate is valid until November 18th.
Parallels Desktop 7 for Mac | Newegg via DealNews