LifeHacker has this and this to say about “flow” (a term coined by American psychologist Mihaly Csikszentmihalyi that means “a condition of heightened focus, productivity, and happiness that we all intuitively understand and hunger for”).

Doesn’t this sound like how most computer geeks spend their time?

In the flow state, Csikszentmihalyi found, people engage so completely in what they are doing that they lose track of time. Hours pass in minutes. All sense of self recedes. At the same time, they are pushing beyond their limits and developing new abilities. Indeed, the best moments usually occur when a person’s body or mind is stretched to capacity. People emerge from each flow experience more complex, Csikszentmihalyi found.

There’s a book on flow and a thread on Ask MetaFilter about achieving flow in everyday life.