Inspired by this SO question, that asks your favorite programming book, which is your favorite book that is available for FREE download.
While I love to buy and read many of those books, I am now looking for books that i can RIGHT NOW download to my system, which I can read while traveling, during waiting for check-in etc.
Here goes my list (all linked to contents page):
Structure and Interpretation of Computer Programs
Note: Language-Specific and Language-Agnostic books, both welcome. Preferably link to the contents page, and provide your review, how it has been useful to you.
Duplicate Questions: