When I was in college I spent a summer going through Alaska's database (it was downloadable), cross referencing with a people search engine, and then mailing letters to people to tell them that they had missing money and how to claim it (and asking for a 5% cut). Made a decent summer's wage. Pretty sure I could have made a ton more money but it was pretty boring work so I just focused on school and more professional internships after that.

Still, an opportunity for someone feeling entrepreneurial out there.