WINE

I am using WINE to run some Windows apps under Linux, and some of them run surprisingly well. Cut to the screenshots, first we have Macromedia Flash 8 (Adobe Flash CS3 doesn't like WINE):















Adobe Audition also works surprisingly well:















I also have Macromedia Dreamweaver 8 working under WINE aswell.
In both of those screenshots, you saw Windows apps running seamlessly under a Linux Ubuntu installation, without the need to run Windows in the background while making it look seamless. Goto winehq.org for more info, download, etc.