Calculate the current estimated dollar value of your home using OFHEO's House Price calculator. Input the purchase price and year, and it'll give you a current estimate.
This is also handy if you want to ponder "what if I'd purchased..." anywhere else in the country. How would your home investment return have compared?
Also check appreciation and average prices of homes in any city or state at the Federal Office of Housing Enterprise Oversight:
http://www.ofheo.gov/HPI.asp
Of course, neighborhoods vary within metro areas, but it's a baseline, at least!