A really good way to learn networking?

I've always found networking the most confusing aspect of everything related to computers. I often wish I had learned more about it. I've tried, but with very little success if any. Can you recommend anything? A course, a page, a book?

A possible starting point: I have four NICs (three wifi) on my machine. I guess I could fool around with some routing... as soon as I learn how.

Thank you for any constructive ideas.

(Note: if you run into this post many years later and you do have a suggestion and I'm still alive, I'm still interested so please reply.)