I was just eyeing the below light at Rivendell. Looks quite effective from the descriptions provided.

http://www.rivbike.com/product-p/lt009.htm

I can't justify the expense right now, otherwise I would pick it up to try it out, I've added it to my list of parts for my touring rigs overhaul though.

I can't really reccommend the light I mounted on the rear of my girlfriends rack, I found out after I bought it that it has a reputation for failures, but hers has been working well, it is quite bright with a little bit of a variation which helps catch the eye. I can't remember the brand/model, I'll check when I finally make it home from work and school later today.