Explorator is a tool for exploring RDF data by direct manipulation. Explorator’s web interface allows users to explore a semi-structured RDF database to both gain knowledge and answer specific questions about a domain, through browsing, search, and exploration mechanisms.
You can access a demo of Explorator here: http://www.tecweb.inf.puc-rio.br/explorator/demo (doesn't work properly in IE).
Explorator has been generalized in RExplorator, allowing parametrization of queries, sharing of solutions, and generating separate user-friendly interfaces. See http://www.tecweb.inf.puc-rio.br/rexplorator.
Enjoy!
The Tecweb Team