BonstioNet is powered by Joomla! and a number of Joomla!. Being the successor to Mambo, its really easy to install, fairly easy to use and really, very extensible. I'd would certainly recommend it to anyone and a great open source CMS.

Some of the better extensions I have used include DocMan and the zOOm Media Gallery. The human readable URLs on this site come courtesy of Artio JoomSEF. The full javascript drop down menu is powered by JoomlArt's Transmenu.