Sherwin Williams Color Visualizer. I use it to perform quick color studies; which helps me to narrow concepts down pretty quickly.
The tool is pretty simple to use. You just choose from one of their preloaded exterior architectural styles; then you paint the scene with colors that you choose from the Sherwin Williams palette. Below is one set of color studies I performed in less than five minutes.
When it's time to repaint your house you might give this tool a try. You can find it at Sherwin Williams Color Visualizer.
One important note: Please put a good size sample up on your wall before you make a final commitment to your colors. One additional step I do at Larson Brenner Architects and Simply Elegant Home Designs is to take my colors and apply them to my 3d house model. You can see an example of that at Architects Have Great Tools!