Figure out best way to display a dashboard with ~6 high-level graphs.
Ok, assuming each graph will have up to 7 points of data per chart and 6 charts per page load. I think the best way is to write a daily number to the database each night in cron. At a minimum, it's retrieving 36 separate indexed rows of data or a combination of simple searches + 6 complex queries to give a real-time estimate of whatever is needed to calculate for that given day.
Also, there is a google charts module for Drupal.