BASE Lab is a search site/tool from the Bielenfeld University Library in Germany that has a couple of very interesting features.
One feature is that it can translate your search terms into different languages using the Eurovoc thesaurus, and retrieve articles from a variety of different foreign-language journals. This can greatly enhance the scope and number of results. Only speak English? Run the search with Eurovoc enabled, then limit your results to English language only. You still benefit greatly from the translated search terms.
The other feature is that you can browse across three hierarchies of the Dewey Decimal Classification. This will only retrieve articles with the necessary metadata, so at the moment it is a fairly limited feature. This could be very promising, an example of a web-based tool leveraging the metadata libraries have been developing for decades.
found via the Web4Lib listserv
