MHM is a tool for discovering sites on same host or IP and for the discovery of sites affiliated to each other, or that might be your competitor. It is available at

http://www.minerazzi.com/tools/mhm/mhm.php

It is great for discovering domain names branded with keywords or known name brands. Excellent also for discovering spam communities, domainers, and more.

You may also use it to build micro-indexes and topic-specific collections (as we do) or to chase down communities of personal interest to law and order agencies, recruiters, etc.