Parallels, the maker of Parallels for Linux and Parallels Desktop for Mac, announced the Parallels Technology Network, a service "dedicated to consolidating the efforts and activities of third party developers who create Parallels Virtual Appliances."
With this new service, you can play around with guest OS images without going thru the hassles of installation and configuration. Other packages include servers such as blog, cvs, mail, wiki, etc., running inside an OS. Check it out! It is a convenient way to experiment on various server installations without messing up your main system.