An interesting play on IaaS for training, demonstrations and development, Cloudshare.com provides you an environment of up to 6 servers on their cloud for free. The key word here is free. You can choose from multiple OS and enterprise software, including Oracle on Windows, CentOs , Xubunto, and MS SQL 2008. Setup is blazing fast, I built a test bed of 3 CentOs servers and a Windows workstation in under 20 minutes. Environments can also be shared with peers and customers through email. They have a paid enterprise offering also for those that need more features. Enjoy!