I'm Ken Krugler, founder of Krugle - a search engine for programmers.
Below is an updated version of my introductory post on the priorart-discuss mailing list.
Krugle is a search engine for code and technical content. Millions
technically oriented web pages, plus source code from repositories,
and 50K+ project descriptions linked to code.
Right now tags (notes) are free-form. They have a name, a note, and then
either a line number range in a file, or an entire file/page.