With a tongue-in-cheek press release, Windows compatibility vendor CodeWeavers announced earlier this week that it would be giving away free licenses and 12-month support for its flagship CrossOver product today, October 31.
CrossOver provides compatibility for Win32 API-based applications like Internet Explorer without requiring a Windows license or installation, which is necessary for virtualization tools like Parallels or VMware Fusion. It's built atop the open-source WINE project. It doesn't support every Windows app fully, but if the one app you need works, it's a solid, low-impact solution.
Originally framed as a voter registration drive, the promotion is now free of caveats or conditions. You can check out the signup page at CodeWeavers' Flock the Vote page.