Building Quality backlinks is one of the most important factors in Search Engine Optimization.
http://www.webconfs.com/backlink-builder.php
This tools help you build a LOT of quality backlinks.
It searches for websites of the theme you specify that contain keyphrases like "Add link", "Add site", "Add URL", "Submit URL" etc.
Most of the results could be potential backlinks.
I use this tool all the time.
It's hard to keep up with all the results they give me though.
It's a great tool for backlinks and increasing your PR.