Looks like a bunch of the INFOMINE project's tools released source about midsummer. As Soumen Chakrabarti advertised there is open source for an honest to gosh focused crawler: the Nalanda iVia Focused Crawler.
I'm starting a quick tire kick. It seems targeted at institutional libraries and is a touch bleeding edge. But hey, it's a potential starting point. Other than Filippo Menczer I don't know of anywhere else to get stuff like this.
Update: A January 2003 paper in D-Lib Magazine gives more context on the INFOMINE project.