This post has more advanced considerations than the ones in my last post, but still things I think everyone* should read. Computer security isn't his job in the airforce; he's just found things out by reading a lot and paying attention.
I think A fair bit of what Glyph has to say makes sense. You don't have to be afraid of the Internet, or spend a lot of time or money, just to feel like you can get along reasonably safely.
My Threat Model - he asserts that the lock and key are a terrible metaphor for computer security, and introduces the notion of a Threat Model.