Why is slavery good? I see lots of references to it's power but I can't find a good article explaining why. To me it seems like giving up long term growth for a short term boost and not a viable strategy.

Slavery is a useful civic. Almost always, you will find yourself hitting the happiness limit cap (because your capital city usually starts in a location with lots of food resources). If it does, you can use slavery to whip away 2 or more population, thus getting a major production bonus while lose a useless pop.

1) Great article!
2) Slavery is very useful, almost overpowered. See http://www.civfanatics.com/civ4/strategy/whip.php