Roelof Temmingh has written a cool new application which provides individuals with the ability to do data mining of publicly available information. It's a cross-platform Java application called Evolution, currently in its second beta, and available as a free download.
H. D. Moore of Metasploit fame raved about Evolution during his packed-to-the-walls presentation at Defcon XV in Las Vegas. It's an impressive piece of work, even if it is still beta, and sports not exactly the most intuitive GUI I've ever seen.
If you're not familiar with the term "data mining," Wikipedia says it "has been defined as 'the nontrivial extraction of implicit, previously unknown, and potentially useful information from data' and 'the science of extracting useful information from large data sets or databases.'"