I stumbled across the MS Bizspark program just the other day, while trying to come up with a cheap MSDN subscription for a startup. It looks pretty good on the surface, and will give you unlimited, free access to most MS software. The interesting thing is that it can be used for production use, not just development purposes (unlike MSDN). It is also for unlimited staff within the company (unlike MSDN which is licensed per each developer).
There are some catches of course:
- You must be a start-up company less than 5 years old
- Your revenue must be less than $1M annually
- The company develops software as it's primary purpose
- I don't think you can use the software to resell hosting services
The membership is good for 3 years, after which you seem to keep any license that you are currently using. They can also put you in contact with other partners for marketing, venture capital, etc.
If you want a look, check out their website. Applications are evaluated on a case by case basis.
http://www.microsoft.com/bizspark/default.aspx
I would call it a 3-year trial