There's also a rather nice chapter in "The Heart of Cohomology" by Goro Kato. It could however be argued that I'm biased since I'm the one who typeset the book :)
Another good starting point is Timothy Chow's "http://www.ams.org/notices/200601/fea-chow.pdf". http://www.ams.org/notices/200601/fea-chow.pdf".

