The Find #1

Before you read the below

A huge collection of free e-books for almost every programming language.
https://ebookfoundation.github.io/free-programming-books

Programming Notes for Professionals

A book composed from StackOverflow answers.
https://goalkicker.com/

The Nature of Code

An ebook and a website, written by Daniel Shiffman himself (The Coding Train).
https://natureofcode.com/book/

EDULINQ

An website and an ebook which teaches all about LINQ, from 0. By Jon Skeet.
https://codeblog.jonskeet.uk/category/edulinq/