One of the blogs I'm always watching for entries is Microsoft's Raymond Chen's The Old New Thing.

Raymond occasionally explains why Windows work the way it works. In addition, he gives insight into why the developers for Windows bend itself backwards, so as to accomodate it's users.

For example, in this blog entry on “Why does the CreateProcess function do autocorrection? ”, Raymond explains the battle between purity and pragmatism, hence giving a rare insight into why (IMO) Windows became the most popular operating system in the world.

Then, in this entry, Raymond explains why the date/time control panel doesn't change the date/time until Apply is pressed, because users use it as a calendar.

In another entry, he goes on about why Explorer ejects the CD after you finish burning it.

Of course, he doesn't always talk about technical stuffs, so it's interesting to read his blog at times.