The National Center for Photovoltaics (NCPV), which is part of the U.S. National Renewable Energy Lab (NREL), maintains a chart that shows efficiency records for all kinds of research solar technologies, from more vanilla to very exotic flavors (thin-film, single-junction cells, multi-junction cells, organic cells, quantum dot cells, etc). Above is the latest version as of April 2013.
On it, you can see the steady pace of progress and how different solar cell compositions compare to each other. Of course, these record-breaking cells were probably very expensive to manufacture and made only in very small quantities, so don't expect to see efficiency numbers like these in commercial PV... But over time, yesterday's record-breakers become today's mass-market products, so all this progress isn't just for the sake of breaking records either.
The high-resolution version of the chart can be found here. Be warned, it's huuuuge.
Via National Center for Photovoltaics at NREL
Note: There's no second slide. I only used the slideshow template because it allowed for a bigger image.
See also: 300,000 mirrors: World's largest thermal solar plant (377MW) under construction in the Mojave