Yobit is good, for volume bittrex and poloniex seem best, I also have used bleutrade and cryptopia to trade once in awhile with good results.
i used all of the above exchangers and i have to say bittrex is the best. but that is just a matter of my preference.
Yobit lists almost any coin, many of them can be scam coins. a lot of them doesn't have any daily volume.
poloneix has the highest volume but it will require personal information for using their site.
bleutrade is a good exchanger with a good API but the volume is not high enough.
cryptopia is also good like bleutrade and low volume but there is this interesting option to trade altcoins with other altcoins instead of btc like trading ltc,doge,ftc,uno,dot,...