Here's the idea: you commit your code to a repository and call a web service (or enter the request through a web app) to have it compiled. The results are then pushed up to a FTP server, S3 bucket, etc. Is there anything like this out there on the public internet?
TFS has a build queuing feature, but I'm thinking more along the lines of a internet (not intranet) web service. And if it can pull from known source control interfaces (Subversion, CVS, etc.) then the caller needs to pass very little besides selecting a compiler and specific compilation options.
My reasoning is more along the lines of removing a lot of software installation and configuration hassles, especially when working between different languages/platforms/frameworks/projects