The cooperative anarchy of the global Internet defies easy characterization or measurement of its behavior. Fortunately, lack of global understanding has not stalled the advancement of network engineering technologies that enable and support Internet growth - for the moment. Both Internet users and providers can benefit from measurements that detect and isolate Internet problems, and identify traffic bottlenecks. Yet it is neither practical nor particularly effective to monitor and measure every single link. Common sense supports the establishment of a measurement infrastructure strategically designed to yield maximal Internet coverage at reasonable cost. However, while individual ISPs monitor their own infrastructure and quality of service, business and other practical concerns often prevent sharing of such information. We survey existing public and mission-specific Internet measurement infrastructures, comparing them using a variety of criteria. Community awareness of similar measurement activities will hopefully facilitate opportunities for collaboration, leveraging experiences and investment across groups. Cataloguing these sources of Internet measurements also provides operations researchers with places to seek topology, workload, performance, and routing data that can help them refine metrics and methodologies for effective management of the global Internet.