What sleep charting software exists for Mac OS X?
I have this one here, very happy with it. 

http://www.fitbit.com/

The last I checked, you can sign up for a fitbit account and use their web application to manually enter sleep times and get nice graphs and statistics using your web browser to see the data.

I don't think there is an export function and it's clearly not a traditional app where all the data exists on your Mac.