Some direct links:

https://github.com/HoTT/book

http://hottheory.files.wordpress.com/2013/03/hott-online.pdf

http://hottheory.files.wordpress.com/2013/03/hott-ebook.pdf

First commit in Nov '12. Most work seems to be have been done since Jan/Feb '13:

https://github.com/HoTT/book/graphs/commit-activity