I am a bit surprised that none has mentioned Cryptopia yet. But maybe it is because they are famous enough so that everybody knows of them?
Anyway I like their interfaces and their deposits/withdrawals are easy and quick. Great place to find altcoins at.
If you havent already seen it then by all means have a look and see what you think about it.
Ref- Link: https://www.cryptopia.co.nz/Register?re ... kryptokoll
They claim to have over 400 crypto currencies and that does not surprise me because I keep finding new coins there everyday. :p
It is based in New Zealand but I cant say anything about their support because I have not had to contact them yet, which in itself is a good sign I guess.
Hope you enjoy it