Reserved Instances on Amazon EC2
Amazon just launched, now only in US area, a new type of instance, besides On-Demand ones available until today: Reserved Instance.
Basically there is a fee upfront for one year (or optionally for 3) in exchange for a discount on the price per hour in the choosen period - the pricing policy did no change compared to the past... but the price did!
An example: A Small On-Demand instance (as it was until now) costs, if always active, about 73$ per month. A Small Reserved instance costs an annual fee of 325$ and then around 20$ per month!!
You can easily understand that if your istance is your web site, your blog or a portal that must be always on, in a year your server will cost you altogether 47$ a month, and therefore the upfront fee makes sense for you... not bad!
For more informations you can follow the links below:
http://www.allthingsdistributed.com/2009/03/amazon_ec2_reserved_instances.html
http://aws.amazon.com/ec2/#pricing
http://aws.amazon.com/ec2/#pricing