We used to call this traction.

Facebook's former VP of User Growth is probably the poster child of this kind of work:

http://www.quora.com/Facebook-Growth-Traction/What-are-some-decisions-taken-by-the-Growth-team-at-Facebook-that-helped-Facebook-reach-500-million-users

Best point: Prioritize Actions by Highest Leverage:

There is a wealth of public data out there for things like email open rates, freemium conversion rates, and more which you would be well served to educate yourself on.

And of course he links to Andrew Chen's article on growth hacking as well.

See my growth hacks stash for more.

Adam Breckler has a Growth Hacks board on Quora.

There he has a link to deconstructing startup growth.

It's clear that most growth hacking happens after product-market fit.

Example: DuckDuckGo. Read more.

See my growth hacks stash for more.

Just found this slide deck, "Think Like a Growth Hacker": http://www.slideshare.net/timhomuth/think-like-a-growth-hacker