Construction vest is #1 at night. I like this style:
http://www.harborfreight.com/reflect...rge-94701.html

The ones with the shiny vinyl reflective stuff doesn't work very well in my experience.

I've updated the reflective vest review I did 5 years ago here (by "updated" I mean I fixed the broken photo links):

http://www.bikeforums.net/showthread...-Freight-vests

What spivonious says about upright position is no doubt true. I only got a road bike this year so mostly in the past I've been pretty upright, I bet I'm a lot less visible when I'm on the road bike, let alone when I'm in the drops.

In the daytime, I run a fairly bright (Serfas Shield, 60 lumens) light on the back. I used to not run a front light, but TWICE this summer I had someone in an oncoming lane pull out and pass another car in my lane, so now I run my headlight in strobe mode. It's a very rapid strobe, like maybe 5 flashes per second, and it's irritating, but people see it. I do point it down a little bit and I have a wide angle lens fitted so it's not blinding, but even so I can see the strobe reflected back from street signs in the daylight, so it's got to be very visible. I can see my taillight reflected back in the rear at night even when I'm quite far past the sign.

Here's a quick video I uploaded to show the reflection:
http://youtu.be/OD1XMUeFAow