lumos2000":w4kug0dd said:http://www.charliethebikemonger.com/pdw-portland-design-works---danger-zone-rear-light-mental-1912-p.asp
I like the look of that one.
I use my LBS and just get the brightest flashing light they have at the time. I've got a couple which are like one half of the Portland design light, and they seem to keep drivers at bay.
I also make a point of positioning the light so that a car close behind will not be able to miss it, so clamped onto the seat post, rather than tucked up under the saddle.