I just posted this on my Facebook wall and realized it might belong in this thread:

If you think you spend too much time on Facebook but don't know what to do about it, try this: set the password to a long string of characters (say, 50 letters or numbers) which you need to manually copy every time, and log off when you finish your session. The daunting prospect of having to manually enter this information will discourage you from logging in unless you really desire it. I went from checking Facebook a dozen times per day to just one or two times. (Tip courtesy of Piers Steel, The Procrastination Equation.)