This thread is a discussion of free Magento AMI on AWS created by GreenGecko. About the AMI: http://www.zetaprints.com/magentohelp/free-magento-ami-on-aws/ It runs 1.4.2, but you can easily upgrade to 1.5. A lot of extensions are still not 1.5 compatible. We keep it on the safe side. Please, give it a try and post your feedback on improvements or additions we should make.
Released new AMIs with magento 1.5 in US and Singapore regions. More here www.zetaprints.com/blog/2011/04/12/web-to-print-in-asia-pacific