You can just type the address of a house into  certain web sites and get market value estimates for it.  Before you rely on these estimates, you need to understand the method behind them and how accurate (or inaccurate) they can be.  This Wall Street Journal article discusses the subject: http://online.wsj.com/article/SB10001424052970204554204577026131448329006.html?grcc=88888Z0&mod=WSJ_hpp_sections_personalfinance