Those who are looking for establishing a hybrid cloud environment(a combination of public and private ‘clouds’) must look at the latest developments happening with Eucalyptus, the open cloud platform. Apart from the elastic computing capabilities, it now has an interface to Amazon EC2 as well(I understand that the latest one is also compatible with S3), making it possible for customers to leverage both internal and external cloud capabilities. I always feel this is an important aspect of on-demand computing environments so that users can get the best services, irrespective of whether the resources are internal or external.
Though I’ve not experimented with it yet(shall do that next week on), this open source environment from what I gather is evolving in the right direction, to become a standards based, hybrid, services based cloud platform and more importantly it’s an open platform, means if you are worried about getting ‘locked-in’, it will be to yourself, a safer bet after all. Documentation on Eucalyptus here for those who are interested.