Pierre,
I think it will really depend on what area in
VO you would like to get rep in. But, I would start by looking at some big name
VO artists (Bob Bergen, Pat Fraley, Julie and so on) and see who represents them. I certainly would not suggest the agent I have in Sac town, but then again I am not a big name dude.
James Alburger has some really resources for this as well:
http://www.voiceacting.com/links/representation/
Good luck,
Jon