Most servers were quickly fixed once news spread. Individuals can check themselves. Here are some exchanges I tested which are fine from the heartbleed attack:

https://sslanalyzer.comodoca.com/?url=coinbase.com
https://sslanalyzer.comodoca.com/?url=bitcoin.de
https://sslanalyzer.comodoca.com/?url=bitsource.org
https://sslanalyzer.comodoca.com/?url=bittylicious.com
https://sslanalyzer.comodoca.com/?url=btc.sx
https://sslanalyzer.comodoca.com/?url=bitnz.com
https://sslanalyzer.comodoca.com/?url=bitstamp.net
https://sslanalyzer.comodoca.com/?url=btcmarkets.net
https://sslanalyzer.comodoca.com/?url=btc-e.com
https://sslanalyzer.comodoca.com/?url=campbx.com
https://sslanalyzer.comodoca.com/?url=bitcoin.it
https://sslanalyzer.comodoca.com/?url=hitbtc.com
https://sslanalyzer.comodoca.com/?url=kapiton.se
https://sslanalyzer.comodoca.com/?url=localbitcoins.com
https://sslanalyzer.comodoca.com/?url=moneypaktrader.com
https://sslanalyzer.comodoca.com/?url=therocktrading.com
https://sslanalyzer.comodoca.com/?url=vircurex.com
https://sslanalyzer.comodoca.com/?url=cavirtex.com
https://sslanalyzer.comodoca.com/?url=virwox.com
https://sslanalyzer.comodoca.com/?url=weexchange.co
https://sslanalyzer.comodoca.com/?url=bitbargain.co.uk
https://sslanalyzer.comodoca.com/?url=btcchina.com


This being said, I see a lot of exchanges with other security concerns that need to be fixed.

Please do not leave your Bitcoins in a hot wallet or exchange until security is taken more seriously. Make the trade and get out.