The Complete Work of Charles Darwin Online. Complete with illustrations, "On the Origin of Species", "The Zoology of the Voyage of H.M.S. Beagle" and every single publication or drawing by Charles Darwin.
"We may all be netted together" - Darwin. This picture is a great way to illustrate and explain the relations/interactions within all animals. Does not necessarily relate to sexual selection, but a good representation of all Darwin theorized of.