An article in the Seattle Times (21 January 2010) states that sitting for a long time, even if you exercise regularly, can be bad for your health.
People who sit most of the day–anywhere–have a higher risk of heart attacks, and are more likely to be fat.
So…where can you stand, rather than sit, during your day? At work? During meetings? Can you arrange your desk and computer so that instead of sitting to work you can stand? Your health may depend on it.