QUOTE(pdq @ Jan 12 2006, 01:32 PM)
Most online vendors only charge tax when delivered to one or at most a few states, so unless you're unlucky you probably won't pay. In addition, there are some states (Delaware for one) that have no sales tax at all, so those residents never pay (I live just over the border in Pennsylvania so I do my major shopping in Delaware).
I'm pretty sure (but not certain) that a lot of states require you (by law) to declare online purchases on you tax return and pay state sales tax on them. Then again a law is only as good as it's enforced, and most states don't have the resources to hunt down the ~$10 in tax you owe them a $200 online purchase.
BTW from what I've seen $200 is generally the going price in a 2GB ipod nano in bricks-&-mortar stores.