Great article on the SciAm website about sleep debt, which is the difference between how much you slept and how much you should have slept.
The trick is that you can't make up for your lack of sleep during weeknights just by sleeping late on weekends, though that's very important too. For proper recovery sleep you need to be sleeping a little extra every day for a period of time till your natural sleep cycle is restored (i.e. your debt has been repaid).
Being a sleep aficionado myself, I can safely say that I already knew that. And having worked in startups for most of my life -- i.e. being someone who swings from periods of no work to periods of intense work which, as you would expect, messes with your sleep cycle -- there are a few other bits of sleep pattern wisdom that I could add. But I'll save those for another blog post since there's lots to say.