Although it is not so closely related to my research, recently I became interested a little bit about Hitchin's fibration and the geometric Langlands program. I have found that many current articles by Frenkel, Gaitsgory, Ngo, etc. are refering to the unfinished book mentioned above, so I though it might worth to read it. However, it refers to many very difficult papers (some of them are in French) and it assumes quite a lot of things. Does anybody know a good survey article, collection of papers, book, whatever which can fill in the gap between a basic, graduate level knowledge of d-modules and stacks, and that book? Also, other introductory resources on geometric Langlands program are welcome. Thanks!