powermonkey has some really good advice above.
My opinion: The Sound Professionals CMC-4U with low sensitvity mod, the Church Audio STC-11, and the Microphone Madness HLSC-1 mics are all good choices for starters. The Microphone Madness mics *may* need modification for use at very loud shows, and does not have interchangeable capsules (i.e. you can only use a cardioid pickup pattern). The SP mics have more capsule options than the Church mics (but between cards and omnis you are covered 95% of the time), and may be better at resisting RFI noise from cell phones etc.
IMO all three of the above are at a similar level of sound quality, but they have distinctive "flavors" and you need to decide for yourself which you like best. Unless you have a strong preference for the flavors of the other mics, the performance per dollar of the Church mics seems the best to me (even though I own the SP mics, I bought them in 2004 which I believe predates the Church mics).