The search function is your friend. And if you've seen how tough it was to find the two posts below you'd understand the humor behind that [img]/images/graemlins/wink.gif[/img]
Here are a couple of old threads that talk about this:
Harrington on Raising
NL Pre-Flop Raising Theories
I didn't re-read these but if you think they are really valuable let me know.