Windows/Mac/Linux: After all that trouble of writing up a step by step tutorial on how to install the software that powers Wikipedia on your home computer, and someone goes ahead and builds a simple click-click-click installer. The BitNami project offers executable installers for lots of open source webapps, from MediaWiki (of Wikipedia) to Drupal to WordPress. Download the installer for the app you want on your computer, and in a few clicks you'll have it up and running—no configuration file editing or installing MySQL, PHPmyadmin, and Apache separately required. Sweet. All BitNami installers are free, and most seem to be offered for Windows, Mac and Linux. Thanks, RIDRU!

Windows/Mac OS X only: Free, open source applications WinLibre and MacLibre install and update a handful of some of the best open source applications available for Windows and Mac OS X, respectively. These are the kind of apps that make setting up a fresh system a breeze—just download, choose the apps you want, install, and you've got most of the software you'd need to get things done. You can re-run the app periodically to check for updates and install newer versions if the apps you're running don't update themselves. Expect most of the obvious favourites, like Firefox, Thunderbird, VLC, Gimp, and Handbrake, along with a few others you may not have known about. Both applications are free. For another Windows alternative, check out previously mentioned InstallPad. Thanks Stephen!