My personal favorite is the Knog USB Boomer Rear. Very bright, easy install and removal, and has some attention-grabbing flash modes. Can be had for around $30-$40. A lot of people don't like Knog because those puny little Beatle lights they sell give them a bad name.
I remember this a while ago before I joined the forums here. Apparently they have a few locations, but I'm not sure if there is an actual retail location.
(found on the Wicked Lasers community: (http://community.wickedlasers.com/index.php?/topic/23660-how-many-addresses-do-wl-have/)...
I agree with Ezeriel. With bike lights, while a wide spread is good for you, too much flood tends to **** off drivers. I've been waiting for the local bike shop to get in the BT10/BT20; these lights are perfect.