BtcChina – The largest bitcoin exchange in China. Currently allows you to trade only in bitcoins. Has two factory authentication, SSL encryption and SMS authentication.
Mt.Gox – A bitcoin only exchange located in Japan. Allows you to deposit funds from almost anywhere in the world but has been criticized for very long account verification times. Currently the 2nd largest exchange after BTCChina.
Bitstamp – Largest bitcoin exchange in United Kingdom. Allows you to trade only in bitcoins. Funds can be added in BTC, USD, EUR, GBP and CHF. Funds can be withdrawn with BTC, EUR, GBP, USD, CHF.
BTC-E – An bitcoin exchange that allows you to trade in many other digital currencies such as litecoin (LTC), namecoin (NMC), Peercoin (PPC), Novacoin (NVC), Feathercoin (FTC) and new ones are added constantly. The site has a Russian and an English interface.
Cavirtex – A canadian bitcoin exchange that allows you to deposit, withdraw and trade in bitcoins. Available to Canadians only at the moment.
itBit – A bitcoin only exchange located in Singapore. An exchange that can be used internationally but account approval for US and Singapore citizens is less strict. Trading can be done with USD, EUR or SGD.
Bitx – A Soth African bitcon exchange that allows you to trade your bitcoins in ZAR (South African Rand).
Fybsg – Another Singaporean exchange that allows you to easily deposit funds and trade bitcoins in Singapore.
Kraken – A new bitcoin exchange with a few extra features such as stop loss, take profit and other limits.
796 – Allows you to trade in bitcoin only and currently accepts OKPAY as a deposit method. Wire transfers for international customers will be soon implemented on this exchange.