The Web Has Many Free Property Records and Valuation Sites
The site zillow.com is the hottest and newest property valuation site on the web. It seems to show up on every blog and Yahoo Group that pertains to public records.
Zillow provides a free home valuation tool which includes square
footage, bedroom/bathroom count, historical information, assessed
value of homes in the area and a satellite map of the property and the
If you are looking to see if someone owns a parcel of land, this page covers most states and counties - Free Property Records Online
Nationwide Environmental Title Research (Netronline) has the most comprehensive collection of both online and offline county assessor, recorder and tax collector contact information.
If the state or county of the property you need to obtain information does not have a free webservice, then I suggest Intelius. The Intelius property report is $14.95 and includes sales history, current value, lot size, property details, owners information, current mortgage, legal description & more.