Not sure what the criteria is for this list is but this exchange was not listed. Is it because their daily trades are relatively low?
https://www.quadrigacx.com/

Interesting... Will it go lower?
http://techcrunch.com/2014/10/04/the-bitcoin-selloff-continues/?ncid=rss&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+Techcrunch+%28TechCrunch%29&utm_content=FaceBook

Just took a look at this and signed up with them. Seems pretty simple compared to the others. Maybe a bit too simple. They're basically validating you via your Visa/Master Card. Not sure how Circle would trust that one from of validation knowing how easy it is to counterfeit or "fake" those cards. Great if you're buying bitcoins and scam the system but shouldn't Circle be more cautious about this?