1. At a Web application on a Web server in a computerized environment, the Web application receiving a request from a requesting computer system for processed content that is based at least in part on non-file-system content source that is maintained separately from a file system located at the Web server that is running the Web application, a method of providing the Web server with the ability to access the non-file-system content source in an efficient manner, and as if accessing content source on the file system at the Web server, the method comprising the acts of: a Web application, receiving a request from a remote requesting computer system for a file that is maintained on a file system located at a Web server that receives the request, wherein the file contains content source and a reference to non-file-system content source, and wherein the request includes an identification of the file maintained on the file system located at the Web server, and an identification of a virtual directory path for the non-file-system content source; determining that the file contains a reference to non-file-system content source that is maintained by an application separately from the file system, the non-file-system content being available through the virtual directory path in the request from the remote requesting computer system; the Web application selecting, after receipt of the request, a virtual path provider, from a plurality of virtual path providers, to provide access to the non-file-system content source through the virtual directory path in the request from the remote requesting computer system; the Web application accessing the non-file-system content source in a manner determined by the virtual path provider such that the non-file-system content source is received as a stream from the virtual path provider through the virtual directory path; the Web application processing the content source with the non-file-system content source to produce the requested file; and storing the requested file as a cache entry in a cache maintained on the Web server.