Here's a fairly new tail light by NiteFlux that looks really interesting. 200 lumens, and the brightness is adjustable not only in solid (15 to 60 lumens) but in flash (10 to 200 lumens).
It also has a very wide beam (two XP-E's with no optics at all).
Multiple flash patterns to choose from.
The light: http://www.niteflux.com/Products_RedZone4.aspx
A thread about it on candlepowerforums: http://www.candlepowerforums.com/vb/...FLUX-RedZone-4
I'm really tempted to order one of these. I like the wide beam width, and the ability to adjust the brightness in flash mode so I can have it really bright in daytime but not blinding at night.
There is also a white version that does up to 500 lumens, looks like it would make an excellent daytime light.