The graphs are pulled from http://bitcoinity.org/markets http://bitcoinity.org/markets which, if you click on the "wtf?" link in the top right, provides an expl

The graphs are pulled from http://bitcoinity.org/markets http://bitcoinity.org/markets which, if you click on the "wtf?" link in the top right, provides an explanation. The line graph shows the current market price of 1 BTC, using the right y-axis which is in US dollars. It's overlaid on a bar graph of trading volume in BTC, which uses the left y-axis.