Yesterday night, microsoft released a public beta of vista. Once downloaded, it will give you 2 licenses which are good for up to 10 computers each. The licences will last for one year.
They have a high demand right now and are bogged down, but you can try later at this address:
Tell us your thoughts of the beta.
Also, you can get a 1 year beta of office 2007 as well to test out.