While I enjoyed reading Soumen Chakrabarti's papers on focused crawling papers, I never got a sense of the dirty details needed to implement such a crawler. I couldn't quite grok the iVia Nalanda source either. The MTech thesis (PDF) of Roger Menezes, a Chakrabarti student, revealed a little more to me. The thesis also explores the potential for "desktop scale" focused crawlers. This interests me because I have a hunch that tagging and aggregators could serve as good mechanisms for interacting with a personal focused crawler.