Use computers to look busy. Any time you use a computer, it looks like work to the casual observer. You can send and receive personal e-mail, calculate your finances and generally have a blast without doing anything remotely related to work.
These aren't exactly the societal benefits that everybody from the computer revolution expected but they're not bad either. When you get caught by your boss--and you will get caught--your best defense is to claim you're teaching yourself to use the new software, thus saving valuable training dollars.
You're not a loafer, you're a self-starter. Offer to show your boss what you learned. That will make your boss scurry away like a frightened salamander.