http://poolpartyrb.com/

• One Ruby Gem = easy EC2 computing cloud

• PoolParty is an open source tool that automates deployment, monitoring, and load balancing of EC2 instances. Configure once, and relax by the poolside — PoolParty will keep your site and its instances afloat.

http://www.rightscale.com/m/

• RightScale’s automated cloud computing management system helps you create scalable web applications that run on Amazon’s Elastic Compute Cloud. Our advanced auto-scaling and load balancing features ensure your site’s uptime and reliability. The RightScale Dashboard makes it easy to setup, launch, and monitor all of your EC2 and AWS activities.
• Pricing starts at $500/mo with $2,500 setup
• Good article: http://blog.rightscale.com/2008/03/26/setting-up-a-fault-tolerant-site-using-amazons-availability-zones/

http://ylastic.com/

• Still in stealth

http://code.google.com/p/scalr/

• Open source
• TechCrunch Article The Auto-Scaling Open-Source Amazon EC2 Effort
• Diagrams: http://code.google.com/p/scalr/wiki/ProcessDiagrams

http://weoceo.weogeo.com/

• Beta
• doesn’t have much information