Want to look up houses for sale in your area, get an idea of how much your house would sell for, and research real estate trends? Try Trulia, a specialized real estate search tool. In addition to what I've already stated, Trulia also offers nifty RSS feeds for specific zipcodes so you can follow which houses have gone up or down in price, Find a Pro, an easy way to find a realtor who meets your needs, and a Mortgage Calculator. Definitely a good resource for anyone who's looking to buy or sell a home.
More real estate Web resources
Craigslist: Craigslist is one of the best places on the Web to find real estate listings, as well as vacation rentals, home swaps, and businesses for sale.
Zillow: Zillow is a great (free!) service that allows you find your estimated home price, along with many other home appraisal services.