Jeff definitely pointed you in the right direction. But I do have to ask - are you looking for appraised value or fair market value? Appraised value is NOT the same as fair market value. If you're looking for fair market value and whether you're getting a good deal (or not), check with your Buyer's Agent.
Btw...If you're buying a new construction home, there is no assessed value on it - there's only land value and estimated total assessed value come tax time.
But you can still find comps in order to determine fair market value. If you're using a Buyer's Agent, they should know how to provide all this information to you.