The MSDN Home page is highlighting the Empower program for ISV's today, since they've just dropped the price to $375 in the US or half the previous price in a number of other countries. Start your sign-up on this page -- not only do you get 5 (count them, five!) MSDN Universal Subscriptions, but you also get the Longhorn preview CD:

Enroll in the Microsoft Empower Program for ISVs by December 31, 2003 to receive 5 MSDN® Universal Subscriptions (one media kit) at the new, lower membership fee and a Longhorn preview CD.

If you have more questions about the Microsoft for Partners program, see their FAQ.