thoughts on productivity
But there's another way of using time that's common among people who make things, like programmers and writers. They generally prefer to use time in units of half a day at least. You can't write or program well in units of an hour. That's barely enough time to get started.
From: Maker's Schedule, Manager's Schedule
Paul Graham's gem of wisdom continue to haunt me as I pound away on my editor.
On a related note, check out Secrets Of Superstar Programmer Productivity: Flow, which mentions the interesting idea, Flow.