Heroshi, open source web crawler. Motivation 1: learn HTTP, libraries, real world quirks. Motivation 2: collection of libraries and tools for building custom crawlers. Motivation 3: provide access to representative subset of Web for educational and research purposes. As of 2012-10-12, last goal is not even started, but these guys did amazing job at it http://commoncrawl.org/ See http://temoto.github.com/heroshi/ for more information.