Have you discovered HomeStyler.com yet? If you don't have time to get completely sucked in, I suggest you avoid it because it is engrossing! I am a total nerd when it comes to home decor and especially rearranging furniture. I am embarrassed to admit that I bust out the graph paper, draw a room to scale, then cut out scaled versions of all the furniture. Then I spend hours positioning and repositioning the scraps of paper until I find a suitable arrangement before I so much as move a rug.
Now there is HomeStyler.com. Start with a room, which you can make completely to scale. Add doorways, windows and closets. It is literally as simple as clicking and dragging elements into place. Now add flooring from the hundreds of choices, paint the walls and start adding furniture. Here's my current living room setup:
The only complaint I have is that there is limited control on things like furniture coloring, but you can just your imagination on that. I don't really have a black leather chair with a red velvet ottoman, but I do have a brown leather chair with a matching ottoman. The versions available work just fine as placeholders.
The usefulness does not end at creating your current rooms and rearranging furniture. You can connect rooms to build an entire house, restaurant or office. Add a yard with landscaping and everything. The possibilities are endless!