They keep doing interesting stuff at the Missouri Census Data Center.
Both the population estimates reports and the new CAPS version are worth checking out. CAPS stands for Circular Area Profiles System (CAPS).
Link to population estimates reports.
Link to ACS CAPS.
This application will aggregate 2007-2011 American Community Survey data to approximate circular areas as specified by the user using a point location and 1 or more radius values. Data used are from the latest tract level 5-year period estimates,