Lights on the bike...

That's very wise of you to have a light. My only wreck with a car came from riding home from a workout a bit too late (dusk, not dark). While I don't have brand suggestions, I just wanted to say that getting a flashing light not only for the back, but also the front is probably the way to make yourself most visible. You do have to consider whether that will distract drivers though.

Your local bike shop or even a sporting goods store should carry what you need. I also recommend trying to wear lighter colored clothing if possible.

A few recent threads on this same question.   Really depends on your budget for the lighting.   REI's had some great sales on the Nite Rider line, not sure if they are still on or if it was a labor day only thing.   I've got a Sol and really happy with it.   For the rear I just picked up a Cat Eye 5 led unit this week and it's -really- bright.  Should be no issue with cars approaching from behind.  

Todd

This was the rear one I purchased.... Cateye TL-LD610.   It's bright enough that it hurts to look directly into the flashing lights.   I think retail on it was $25.    I just wanted one that mounted to the seat post as opposed to the belt clip things.    

Check out instructables.com

There are some very inexpensive, yet highly effective solutions there.  I love to make my own gadgets, so its as much fun as it is function for me.

I've also bought some 3w LED flashlights from Sam's and configured conduit hangers to clamp onto my bars.  I aim one higher to reach out and illuminate the road ahead, and another lower to flood the area right in front of my front tire.  It works really well.  I haven't used it since last spring though.  I need to dig it out.