Scoble sums up his travel advice with this:
Anyway, the new rule we recommend? 1:30 for any domestic flight and three hours for any international flight. If you can add more, do. There’s nothing more stressful than seeing a super long security line or, worse, being caught in traffic on the way to the airport knowing you are about to miss the only flight of the day.
Maybe I'm just lucky - I never allow that much time at the airport, unless the airport in question is Heathrow (it's often miserable to get through). When I fly from BWI, I usually don't leave the house until an hour before the flight, leaving 40 minutes or so at the airport.
As to what he says about checking bags - the best advice I can give is this: make it fit in two bags so that you can completely avoid baggage check. Nothing adds time to your trip like checking and retrieving bags.