[Disclaimer - I work on Windows Azure]

Microsoft also offers a free promotion to all new subscribers (click "view details" link under "Buy Now" button): http://www.microsoft.com/windowsazure/offers/

From the site:

Included each month at no charge:

* 25hrs small compute instance

* 500MB storage

* 10,000 storage transactions

* SQL Azure 1GB Web Edition database (3months only)

Any monthly usage in excess of the above amounts will be charged at the standard rates. This introductory special will end on March 31, 2011 and all usage will then be charged at the standard rates.