Click2Try: Test dozens of open source apps from your web browser
You'll need Java and a relatively modern browser in order to run the applications. Firefox, Internet Explorer, Safari, and Google Chrome all work. You can try any application for free without registering. If you want to save your sessions you'll need to sign up for a free account. You can also purchase a subscription if you want to access an application for an extended period of time or run more than one application at a time.
Click2try's catalog includes Ubuntu, OpenSUSE, and CentOS Linux distributions and applications including Chandler, Filezilla, OxygenOffice, WordPress, Drupla, and Joomla.