Zillow.com came around a couple of months ago (still in beta mode). Founded by the same owner of expedia.com, I have to say the technology is state-of-the-art.
If you have not tried it out, you definitely want to check it out. I just punched in my address in the textbox, and within a minute came the sales comps - Amazing! It will even tell you how much your neighbor's house is worth, muahahahaha...
This is defintely the coolest FREE tool on the internet right now for us home owners, to-be home owners, and people who are thinking of selling their homes, and do not have the slightest idea how much the house is the worth.
It is also a great tool to get a general idea who much a neighborhood is running for. It is especially useful for me because I invest in out-of-state properties and it gives me the house value chart for the past 1 year, 5 years, and even 10 years.
Being a realtor myself, let's just say this tool can put the appraisers out of business! Who needs appraisers anymore when you can Zillow it yourself!
Go to Zillows real estate appraisal