These people are selling some good products.  No it doesn't have anything to do with computers, networks, or programming, but its still a good read.  If you just want to take my word for it you can buy the books directly from http://rpg.drivethrustuff.com/index.php?filters=0_0_0&manufacturers_id=782

While the main focus of this website is the SpinRite program there is much more to it.  The Services and Freeware sections have several useful nuggets.

A simple site with some tools for diagnosing email issues.  The blacklist check and the mxrecord lookup can prove useful.