This online annotated bibliography corresponds to the American Journal of Physics Resource Letter "Gravitational Lensing" by Tommaso Treu, Phil Marshall and Douglas Clowe (2012). It is maintained by us, the authors, and represents our own opinions and biases. The browser title "Best Content in Gravitational Lensing" may therefore be misleading! If we have missed a link that should be posted here, please do get in touch by email. A PDF version of the 2012 resource letter can be obtained from the arxiv.