There is a small but very usable program I've been using for quite some time and I highly recommend it. You might look into it on:
Also, if you are looking for something more robust and complex:
I've used their 3D Home Architect as well, recommendable tool. Still, due to the high price (99.99$!) I'd stick with Room Arranger.
P.S. I know what has crossed your mind when you read that second link ;-) : Prince of Persia!
P.P.S. Check your Private Messages!