Wine is a great way to run your favourite Windows programs on Linux, but if you don't want to mess with a program's settings to get it just right, free app PlayOnLinux has a bunch in its database that you can install with one click.
PlayOnLinux uses Wine to install these programs, so you aren't getting some half-arsed emulation here — this is just a way to quickly and easily install your favourite apps from one simple menu. It has many games, from Starcraft II to Portal, plus other popular Windows apps like Microsoft Office. Essentially, it takes the technical, behind-the-scenes work and does it all for you, so you can get to using your apps. It'll even install the best version of Wine for each app, meaning you always get the best experience possible. Hit the link to check it out, and see the How-To Geek link for a more in-depth guide on what else it can do.
PlayOnLinux is a free download for Linux systems. It's available in the Ubuntu repositories, too, so you can just grab it right from the Ubuntu Software Center.
PlayOnLinux [via How-To Geek]