We have a program that we bought back in '97 or '98 for designing houses. It's called 3D Home Architect and is put out by Broderbund. I'm sure they have a newer version by now, but we used this one to draw up a floorplan when we did a total remodel on our old home (only thing 'original' to the building afterwards were the foundation, floor joists, four outer walls, roof and one interior wall!!). We also used it to design our new home that we built ourselves. Our version will do print outs of floor plans and elevations, but not blueprints. But it sure was handy to go to an architect and hand him the printouts saying "here, this is what we want, draw it in blue so the bank and building permit people will be happy". Saved quite a bit of money versus having to hire an architect to sit with us and find out what we wanted.
Now that the house is built, I'm interested in finding a software program for landscaping. I think there are some out there with the capabilities to input your own house so you can see exactly how different landscape schemes will work for you, but I haven't seen those programs myself at this point.