I know that NC and DC have tax free weekends in August/September usually where school supplies (including computers) can be purchased without taxes. Saved me $100 when I had to buy a laptop last year. If you need to buy one, might want to check if those deadlines work for you.
fwiw, from wat i hear, windows vista is not worth the wait
Apparently the next generation of Windows is coming out this Fall too. It seems pretty lame to have to buy a laptop and then have the next generation come out in a couple months, but that may happen.