Marie at Disarranging Mine has a post up about accessing public records online.
I’d just like to add to this discussion a link to a site, Pretrieve, where you can get public records from around the country, including a number of Illinois counties (Sangamon is NOT one of them, however). It's free to use.
I was able to track a number of court proceedings against my ex-wife who, in another county, continues her life of crime (recent orders of protection against her, small claims judgments, a criminal telephone harassment charge – all the same stuff that I knew her for late in our marriage).
Pretrieve is a little hard to use (I think) but with a little persistence and clicking around, you can find out quite a lot about people living in places that have public records online.