The United States government site, https://www.usa.gov/unclaimed-money as of this writing links to https://www.unclaimed.org/ which links to http://missingmoney.com/
The Indiana State Government site, https://indianaunclaimed.gov/apps/ag/ucp/index.html currently has its own system. You may want to check with different states.
Good luck getting to the point where you can get results at http://foundmoneyguide.com They ask you a bunch of questions that have nothing to do with getting results before they deliver, if they deliver... I never got that far.
I inserted my name into a set of fields at http://go.neverclaimed.com and got a wait bar that said unlocking millions of records. Then I got a wait bar that started counting down from about 42 seconds.Then I started typing this paragraph. Then it wants you to sign up for an account. I didn't.
Wait... Just scrolled down their page a bit more. They offer a 100% money back guarantee. Mighty generous of them considering they haven't asked me for any money yet, but where there's a money back guarantee, there's money out!