Thanks to Nicolas, I found this nice search engine, called, iSpecies, which core idea is that web results can be grouped according to the species of the document. The engine uses several data sources, hacking on the aggregation and clustering of the data:
iSpecies uses web services to talk to source databases, extract data, and assemble a page for each species. The code makes extensive use of XML. Essentially, each web service returns XML in one form or another, and I use and XSL style sheets to transform the result into HTML.