I also keep one of these in the bag. USB rechargeable so I can plug it in at work. I like to have two lights;
http://www.sierratradingpost.com/kno...processed=true
One with all the lumens that slightly points down so I can see potholes and train tracks and stuff.
The Knog, which is not as bright (but read the listing because some of them really are! So they are an affordable option) points straight ahead. That one says to oncoming traffic "Hey! I'm riding here" but does NOT blind them.
Also have rear lights and I do not use blinky lights for reasons we have discussed over pizza and beer; http://forums.teamestrogen.com/showthread.php?t=12261