Columns in an ignimbrite on the east side of Santa Maria volcano in Guatemala. (A drive-by, unfortunately. I would have loved a close-up look at these!)
Some of the oldest volcanics in the Vulsini volcanic district, Italy: a jointed trachyte from the Bolsena caldera complex. (The tree at the top of the cliff is about 3 m tall.) This is one of my favorite photos, because you can see multiple cooling sets divided by fractures - and it really emphasizes how columns form from inward-directed cooling.
And, finally, an actual example of columnar jointing in basalt, which is probably much more common than jointing in an any of the other stuff I've mentioned: a lava flow near St. George, Utah. (Wish I could figure out where, but Google Earth isn't helping today. Has anyone seen this abandoned water tank?)
Perhaps we should submit a request for a Columnar Jointing Week to someone in Washington. As far as I can tell, we're sadly lacking in geological observances anyway...
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