I upload my nightclub/event photos to dontstayin.com, although they don't act as agents til you become a "Pro Spotter". Tillate.com treat their photographers fairly well and interview before signing them, but they expect you to sign over your copyright.
My advice would be to suck up to every promoter you can find, via email and face-to-face. That way you build your own reputation rather than relying on an agency that will be handling lots of other photographers.
Your work is good, let people see that (links in every email you send, etc).