On sept. 21 2009 the Astronomy Picture Of the Day was a magnificent image from Hubble's new SM4 camera, showing a gravitationally lensed galaxy in stunning detail. The first link in the description points to a review paper "ARC(LET)S IN CLUSTERS OF GALAXIES" by Bernard Fort and Yannick Mellier, I think from 1994.
I just read the introduction section, and found it to be a very readable, and very interesting description of the history of our understanding of these objects. Can't wait to read the rest. Also a great example of how seemingly unconnected discoveries can help answer other questions. Compare this image to the one on APOD. It's probably old news to anyone in astronomy, but maybe worth a look for those who, like me, have only a rudimentary understanding of how this works. The new images are stunning, but having a sense of the history (of only 20 years!) makes them even more so. To me, anyway. Thanks, APOD people.