You all see Ditech's ads in the cable: it promises to give you a great loan by toll free number. I am not recommending its loan products because they are simply too expensive compared to those you can get from a more competitive setting like LendingTree.com or BankRate.com. However, its web site offers an interesting service: Free eAppraisal.
By simply typing in an address, the service can quickly show you the most recent sale price on the property, plus a range of estimate of its current value. Based on my testing of a few address, and comparing the results to those I can find from public records, it seems that what this eAppraisal service does is to pull out the most recent transation price of properties in the neighborhood, and show you the range of the highest value and lowest value.
Of course, you cannot expect this free service to offer the same amount of information as a formal appraisal, which can easily cost you $300 to $400. I feel this service provides some value because you can easily get the last sale price and a fact-based price range, especially when you are not sure how to get to the local public records library to get the same information.