Hello,
I have an idea about semantic web: linked data. The linked data is built behind semantic web ideas. Including Sparql, ontology & vocabulary, etc. The implementation is to build system that create a SPARQL endpoint, crawling data from Internet, put it into Sparql, and publish it. For instance, you can crawl events from lastfm, then publish/allow the other applications access by using sparql language or browser. All the implemtation can be done by JAVA.
If you feel interest, feel free contact me.
Thanks
Chu