I would like to recommend you a blog that I find very interesting: it's called The old new thing, and is published by Raymond Chen. You know, I'm not a Windows fan... and this blog's main subject is Windows... so why am I recommending it?

The articles in this blog explain curiosities about why Windows behaves the way it does in some scenarios, how some features are implemented, what is considered when making some decisions, why some things that look strange (in the API, for example) are done that way, etc. Moreover, it also shows some programming tips and also includes some non-Windows related articles. Enjoy it!