When I searched and bought my current house one year ago, I feel quite helped by the multiple online resources. Using search engine provided by major real estate agencies like Windemere and John L. Scott, I could search available listings by the name of the city, and finetuned my results by adding creteria like size of living space and offering price range. The only headache was: sometimes I didn't know where the house is from the address; this didn't bother me too much, as I can always consult Microsoft Streets and Trips to get the exact location.
Now someone is challenging the status quo: a new search engine, Redfin, now provides map-based real estate search for Seattle-East Side metro area. Redfin's property search interface starts with the complete aerial image of the King County, WA, and allow you to drill down to specific areas of interest. At any time, you can click a button and have available properties highlighted in the map (and add price range and room number restrictions if you want). Clicking a highlighted property and you will be shown the pictures, discription, property tax information and sales price history. (Now you know what your seller paid for your next house.)
What's more, there is an option to search for similar recent sales in the last six months -- results are shown on the map with the different color. With this powerful feature one can almost do the CMA (competitive market analysis) on his own.
I am also amazed by the level of details Redfin's aerial imagery displays. At maximal resolution, my house is almost half inch tall and 1/3 inch wide (approximately the size of the "P" in the PFBLOG.COM title). I can even see a car was parking on my neighbor's driveway.
This is what I called the ultimate real estate search engine. If you live in the Seattle/East Side area and want to buy your next house, give this free service a try!