photo from National GeographicYeah, sure, that Icelandic volcano whose name no one can pronounce is wreaking havoc with air travel, but it sure is putting on a show!
The photo here is of the eruption of Chilean volcano Chaiten, but volcanic lighting was documented way back in 79 C.E. when Pliny the Elder gave his description (and his life) to the eruption of Vesuvius. (Pliny is the reason explosive volcanic eruptions are called "Plinian.")
At any rate, all this info is an excuse to link to the fantastic (in every sense of the word) photos of volcanic lighting.