The above graphic, passed along by the Huffington Post's Laura Bassett, was put together by the Enliven Project using data from Department of Justice's National Crime Victimization Survey and FBI reports. It drives home extremely well the fact that false rape accusations are exceedingly rare, despite what media reports might suggest. Almost as rare are cases when rapists actually go to jail.
Update: Rape statistics are notoriously hard to collect, and Amanda Marcotte has a compelling critique of the methods used here, which Enliven describes in more detail here. So while the phenomena described here are real (and Marcotte argues that, if anything, the chart exaggerates the number of false accusations), be aware that the exact numbers are subject to dispute.