@craftywoman : Merrick likes to sell houses fast, so I think they'll tend to start on the low end. That said, property values around here HAVE fallen dramatically in the past few years, so a lot of people selling property now are shocked at what their property is worth.
I second what others have said - check on zillow.com, or a similar website. Look at your house's estimated value, and (perhaps more importantly) look for comparable houses in the area that have sold in the past 2 years. Try to find houses that are similar in size, layout, and state (remodeled, or needing remodeling). Just like on ebay, people can ask whatever they want for their property, so you can't really gauge accurate values from the asking prices. You need to look at the selling prices to know what the true value of a property is.