Btc-e and Bitstamp are already working I think, Coinbase for US based?, Circle is quite new and don't know allot about it.
Coinbase has recently started doing businesses in 18 European countries.
https://www.coinbase.com/global I'am also interessted if there is any website to buy using Paypal maybe ? or MasterCard
You may try Virwox to buy bitcoin with Paypal.
Any idea about the rates ? 1:1 ?