Amazon have announced Micro On-Demand instances for Amazon EC2.
Pricing starts at $0.02 per hour for Linux and $0.03 per hour for
Windows and the instances are available immediately in all regions.
Micro On-Demand instances provide 613 MB of memory and support 32-bit
and 64-bit platforms on both Linux and Windows and could prove ideal
for less demanding applications.
Full details can be found at http://aws.amazon.com/ec2/