property value

The value is a matter of a price opinion to an individual. If you asked 10 realtors or 10 appraisers, you could get 10 different answers, although you should be able to zone in on a range.

A Realtor could usually give you a fair market value without paying for it, with hopes that if you do sell, that you give the realtor an opportunity to list it.

Otherwise, paying an appraiser is also a great way to find out.

Which route to take probably depends on what you are trying to do: sell or refinance.

Thanks so much for the thoughtful answers!  I was hoping there was somewhere online where I could calculate an estimate... someone told me this site did that but apparently not!  Thanks, anyway, though!

The Wall Street Journal reported January 31 that Home Prices Sink Further - Declines Reported in All 28 Major Metropolitan Areas; Unsold Inventory Piles Up
"Home values are falling at an accelerating rate in many cities across the U.S.  The Wall Street Journal's latest quarterly survey of housing-market conditions found that prices declined in all of the 28 major metropolitan areas tracked during the fourth quarter when compared to a year earlier."
Can you afford the list, wait, and continuously reduce method of selling?  Do you want to continue to pay the current mortgage, insurance, taxes and maintenance and upkeep of the property all while your property continues to become worth less?
Do you want to be just one of the many properties listed that continually has the price negotiated lower and lower?
How can you find out property value? 
Have an auction! 
Force the market t bring the reality of what your property is worth with qualified buyers who will compete to buy your home!  This is what "traditional" real estate sales with an Agent/Realtor/Broker is not capable of doing.
You may hear people tell you to "list" the property at a "realistic" price.  What exactly is realistic?  Once you put a price on the property it only gets negotiated down. 
So what can you do?
You have several options.
1) Use the list, wait, reduce, wait and continuously reduce method of selling where you tell the world what you are willing to settle for by putting a price tag on your property.
2) Use the auction method where only you and the auctioneer know what you will accept and make a decision the day of auction if you want to take the highest bid and have qualified buyers compete to purchase your property at fair market value.
3) Try to do it all yourself.
The auction method is the cleanest and most true and tried method of easily selling real and personal property in the world.  The auction method dates back to B.C. and is the method that over 90% of real property is sold around the world.  Auctioneers have kept it all simple for centuries where they help their clients reach their goals.  Auctioneers are not paying lobbyists to buy off legislators to eliminate other methods of selling like the funds paid by Agents/Realtors/Brokers - example: New Jersey.
There is a real and viable alternative for property owners today to find out what their home is worth and many are becoming one the wiser to realizing that there is a way to actually know when their real real estate will be sold where they have qualified buyers compete to own the property at fair market value...
View the video report about "The U.S. houseing market may take five or six more years to recover, TrimTabs Investment Research warned recently."
So can you afford to use the list, wait, reduce and continuously wait while reducing and settling for less method of selling while your home becomes worth less and less?
With the the Auction Method when buyers compete, sellers win?

The easiest way would be to have a local realtor create a competitive market analysis for you. Most will do this for free. Or you can look up recent home sales of comparable homes in your neighborhood.