Gridspot can link up idle computers (instances) across the world to provide large scale efforts with the computing power they require at affordable prices (0.1-0.3 cents/CPU hour).
These Linux instances run Ubuntu inside a virtual machine. You are able to bid on access to these instances and specify the requirements of your tasks or jobs. When your bid is fulfilled, you can start running the instances using SSH anywhere you'd like. There are grant options available to defray costs for researchers and non-profits.
The Gridspot API allows you to manage instances and identify new ones. You can list available instances, access them, and stop the instances if you so choose. Each API call requires an API key that can be generated from your account page