Amazon EC2

Amazon elastic compute cloud (EC2) is a web service from Amazon which provides affordable cloud computing for your applications. With EC2 simple web interfaces you can easily configure the resources on the fly.

Review:
In past EC2 had some stability problems, but since 2008 it seems to be quite matured and reliable. Many large scale services are now leveraging EC2 instead of setting up their own infrastructure. Some of the well know services running on EC2 includes Rackspace (email & apps), Zmanda (Open Source Backup), 37Signals and many more.

Related reading:
1. IBM Apps running on EC2 - read more..
2. Amazon EC2 product page - read more..
3. Case Studies - read more..