Hang out on the Mic board at this site for a while and you'll learn alot about mics. However, with a general quetion like "what's the best mic?" you will get very many different opinions.
As DJL indicates, it depends on budget, pre amps, type of voice, etc. etc.
If you are looking to buy your first mic, a Shure SM57 (around $80) would be a good start. Although it is not technically a "vocal mic" it is a good multi use mic (which can be used on vocals) that also works good to mic guitar cabs as well as snare drums and tom.
Normally, the best "vocal mics" are condensor mics (vs. a dynamic mic - such as the SM57). However, these normally arel a little more costly ($150 and up - although they seem to be getting less costly all the time), and require 48v "phantom power" - which I do not beleive you can get from your POD.