Mondriaan appears as a little icon with four colors in the upper right corner of your Mac OS X menu bar. You click on each of the four colors to get to each set of bookmarks through a menu. Clockwise, this is: Favorites: white, Explore:red, Friends:blue, FTP Servers:yellow. Use Control-Click on the Mondriaan icon to get access to the Daily set. The Daily command opens a set of bookmarks in multiple browser windows simultaneously.
You need URL Manager Pro to edit the bookmark sets. By default, Mondriaan shows one list of popular Web Sites, including AltaVista, Google, several Macintosh news sites, travel sites and Apple's download page.