1. A system, comprising: first and second federation servers each being connected to a set of computing resource providers and each of which are connected to a set of computing resources, the first and second federation servers each being configured to determine which computing resources are allocated and which are available to users who issue on-demand computing requests; and wherein the first federation server having a computer-readable federation catalog which lists the second federation server, and wherein the second federation server having a computer-readable federation catalog which lists the first federation server to which the second federation server maintains communication to either request a computer-readable catalog of computing resources of a computing resource provider connected to the first federation server or communicate an on-demand computing request to the first federation server.