SketchUp is a great general purpose design tool, but it's not very good at home and landscape design.
I've been developing web-based home and landscape design software at
www.MyGardenPlans.com. Its very new, but I'm releasing updates almost every day. Your feedback is appreciated.
I've designed the software to be very user friendly. It feels a lot like SketchUp, but it's intended primarily for home and landscape design users. Creating walls is similar to that of SketchUp (e.g. snapping to lines and right angles), but MyGardenPlans.com shows the length and thickness of the walls and doors. The software also has a drag and drop plant database.