Several core reports (as well as some reports provided via extensions) use the OpenFlashChart library to create nice looking charts via flash.
Unfortunately (or fortunately depending on how you look at it), flash is on the way out. Many browsers disable it by default.
Has anyone worked on a drop-in replacement for Reports that use html5 or javascript or anything but flash? I know about Xavier's CiviVisualize which looks very promising, but it's not clear how to use it in a report to replace the chart functionality provided by OpenFlashCharts.