This is an interesting article about how the bad economy has made people more aggressive in pursuing unclaimed property. In most states, unclaimed property is accessed via the state's treasurer -- that's the case in Illinois as well (go here for the state's site).
And, as the website mentions, the property might not be just in your name -- check for deceased relatives as well. However, the article is right to mention that you'll want to do a cost-benefit analysis to determine whether it's worthwhile to collect the property. I am working with the Illinois state treasurer on two estates involving unclaimed property, and let me just say that it's a lengthy process (not that I'm blaming them -- they don't want to be in the position where they pay the wrong people). You may need to present a small estate affidavit or even open a probate estate for a deceased person. And you also may need to present evidence of the decedent's address. All of this means you'll want to make sure that you'll be making money on the transaction, not losing money.