Almost all dynamo hubs produce the same power, 6v, 3w, .5a, so they are all compatible with the lights that are also almost all to the same spec. The spec itself is the German StVZO (or is it StZVO?). The other brands to consider are SRAM, Sanyo, S-A, and Shutter Precision as already mentioned. There are some dynamos that don't produce to this spec but they aren't taken seriously. As far as rim size, there are some that are meant to be used with 20" rims for folding bikes, otherwise 26, 27 or 700c are all compatible.

As far as the brands, only Schmidt seems to make both dynamos and lights.

There really isn't a lot of info on these things, but there are a few pages. The google and siri know everything.