arcsynthesis.org (the site mentioned in the accepted answer) seems to be down and out, unfortunately. (EDIT: it is available at this link!).
Anton Gerdelan's tutorials for OpenGL 4 are very readable and up to date as of mid-2014. The first few are free, the rest are available on amazon, where they have great reviews, for a small price. So far I've been pleased.
There are some more free tutorials for OpenGL 3.3+ at http://www.opengl-tutorial.org/. They date back to 2012, but may be good supplemental material for other sources.