Ebot, an Opensource Web Crawler built on top of a nosql database (apache couchdb, riak), AMQP database (rabbitmq), webmachine and mochiweb. Ebot is written in Erlang and it is a very scalable, distribuited and highly configurable web cawler. See wiki pages for more details
now ebot works only with a couchdb server running in localhost hostname, user and password should be put in priv/ebot_db.conf