Marketplaces with an API
URL trade fee $ in fee $ out fee
MtGox.com 0.6%
https://mtgox.com/fee-schedule
BitStamp.net 0.5%
https://www.bitstamp.net/fee_schedule/
Intersango.com 0.65%
https://intersango.com/fees.php
BTC-e.com 0.2%
https://btc-e.com/page/2
BitMe.com 0.6%
https://bitme.com/

http://bitcoincharts.com/markets/