Chris pointed out Jeff's blog about the Iron Triangle.
I've got a slightly different take on the situation. The phrase, "Good, Fast, Cheap . . . pick any two" is highly applicable in any conversation about resources or timelines.
Good + Fast = Expensive.
Good + Cheap=Not Fast.
Fast + Cheap=Not Good.
As you can see, quality, time, and resources and functionality are all implied by this. I would point out that Functionality and Quality are roughly equivalent.