1. At a client computer system including at least one processor and a memory, in a computer networking environment including a plurality of computing systems, a computer-implemented method for rapidly launching a virtual software application using on-demand file staging, the method comprising: an act of creating, on the client computer system, a high-level file listing that includes a list of specified high-level data files and directories that are part of a virtual application package; an act of receiving an indication from an application user that the virtual application is to be accessed; an act of dynamically creating sparse data files for those data files that are to be accessed based on the received indication, the sparse files including file names and file sizes for those data files that are to be accessed, the data corresponding to the sparse data files being stored in a remote data store; and upon determining that the virtual application is attempting to access one or more of the sparse data files, an act of dynamically streaming the data corresponding to the sparse data files on demand from the remote data store.