Get a Bright Bike kit from brightthread.com:
Bright Bike DIY kits cover your bicycle in easy-to-apply design-savvy ultra reflective vinyl for safety. It is like covering your bike with a big stickers that turn ultra-bright in headlights. The retroreflective vinyl is the same material used on the backs of running shoes, but with colors. The kits greatly improve night visibility and thus bicycle safety.
These kits are pre-cut and easy to put on.
I got the blue pinstripe set and I love it - a bright source of light, like a car headlight, hits your bike, and you light up like a christmas tree. It's especially pronounced at night, and as cool as this picture is, it doesn't do it justice. Check out the video on their website for a nighttime demonstration.
Edit: I thought I would share my picture of my bike with the blue BrightBike pinstripes on it. This is taken in my dark garage with my flash covered (just enough light to make it glow without the picture being blurry). In daylight, the color is almost the same as my paint color, so they're hard to see.