I think a lot of it depends what currency you are using to buy the btc. For AUD I've heard positive things about https://www.coinjar.com/, for USD I've heard that https://www.bitstamp.net/ is alright. I am not making any claims about either - just heard from others that they have been decent to use (quick, alright customer service).

This market list might help - http://bitcoincharts.com/markets/list/