1. A system, comprising: first and second federation servers each with a set of registered computing resource providers, wherein a computing resource provider offers computing resources in different software and services consumption models including Infrastructure as a Service, Platform as a Service and Software as a Service, wherein the computing resource provider offers information on what types of computing resources are allocated and what types are available to be allocated to registered users who issue on-demand computing requests; and wherein the first federation server is unified with the second federation server such that the first federation server has a computer-readable federation catalog that lists computing service providers and their computing resource offers to satisfy the on-demand computing requests, wherein the federation catalog of the first federation server lists the second federation server, when registered, as a computing resource provider, and wherein the federation catalog of the second federation server, when registered, as a computing resource provider, lists the first federation server, when registered, as a computing resource provider, wherein the first federation server provides an interface that, on request, provides updated, computer-readable catalogs of computing resources and computing resource providers linked to the first federation server, wherein the second federation server maintains communication with the first federation server to request an updated computer-readable catalog of computing resources and computing resource providers registered to the first federation server, or communicate a user's on-demand computing request to the first federation server or list, provision, use, and manage resources for an on-demand computing request addressed by the first federation server and the computing resource providers registered with it.