floorplanner.com offers a really nice on-line flash program that allows you to do floor plan designs on-line. The software is really easy to use, right in your browser, and it's amazing how quickly you can do a design. They offer a lot of design elements that are canned, which also helps with creating a design. In addition to laying out the floor plan, you can add furniture too so that you can get a better idea of how much space there will be in your floorplan. The service they offer is free, and you can share your designs with others.