In addition to lights, there is also a very cool (imo) hyper-reflective tape called SOLAS made by 3M. This stands for Safety Of Life At Sea, and is the highest grade reflective tape you can get. Although no tape is going to be as bright as a battery or generator operated light, reflective tape can complement your lighting system to make you even more visible. Plus using tape is a lot less uncool than reflectors and gives you a bit of room for creativity.

I bought some black solas tape and use the black on the back of my black messenger bag. Can't even see it during the day, but I like it because the safety triangles that I cut-out shine back at night. I also put solas tape on the front of the handlebars, on the seat-stays, a bit on the top tube, definitely the crank arms, and I have a set of wheels with solas taped to the rim in between spokes. I probably look like a clown in the headlights of a city garbage truck, but better that than roadkill.

SOLAS can be found by searching google or eBay. Get the thin flexible kind.