Today Microsoft announced BizSpark: http://www.microsoftstartupzone.com/bizspark
This program gives ISV startup with less than USD$1m in annual revenue (lower amounts for some other countries - for example it's just USD$250k for Egypt) free access to MSDN subscriptions. Nice. You get Visual Studio, Expression, VSTS, SQL Server, BizTalk Server, SharePoint Server, Windows Server - all you need to build a software app on the Microsoft application platform.
There are some requirements: you have to be a software startup, privately held, and there's the revenue limit. If you don't qualify for that deal, there are others that may work for you. Here's a summary :