"Threading in C#" is a free e-book, available at Joseph Albahari's website.
From the basics questions when to use and when not to use threading to the more advanced stuff. You can read it online or download the pdf (429Kb).
The content of this site are my own personal opinions and do not represent my employer's view in anyway. In addition, my thoughts and opinions often change, and as a weblog is intended to provide a semi-permanent point in time snapshot you should not consider out of date posts to reflect my current thoughts and opinions.