The good folks over at Information Aesthetics
recently posted a link to Wiki Mind Map
. The site provides a mind-map-style outline of topics in Wikipedia
Right now the site appears to be able to search the German, English, Spanish, French, Italian, Catalan, and Indonesian versions of the encyclopedia. It can also search www.self-qs.de, which appears to be some sort of German dictionary (perhaps a German-speaker can help out here).