Is there any online tool for learning openings?

This site can walk you through the first 5-10 moves of many openings: http://www.eudesign.com/chessops/index.htm . To actually understand an opening, though, the most important thing is to understand the reasoning behind each move, for both sides, and to understand what types of middlegame positions tend to result and what sort of strategy each side should pursue at that point.
First though, I'd strongly advise you to read some of Dan Heisman's "Novice Nook" columns at chesscafe.com. Here are two good ones on openings:
http://www.chesscafe.com/text/heisman37.pdf
http://www.chesscafe.com/text/heisman53.pdf

Is there any online tool that would walk me step by step through an opening? I've never really learned some structured opening. I simply try to get all my pieces out as soon as possible to have plenty of options later.