In the Avengers, there is a obviously very complex, high-tech organization called S.H.I.E.L.D. Where do they get their funding?
S.H.I.E.L.D. (Strategic Hazard Intervention Espionage Logistics Directorate) is a United Nations funded covert unit with a secret council who direct and controls its operations.
SHIELD has been described over the years as a United States covert operative agency initially but later revised to be a United Nations organization because of the international nature of the threats against it. HYDRA and AIM are both agencies with international funding and support as well as bases of operation. SHIELD would need a similar kind of jurisdiction to be able to effectively counter their operations. SHIELD works with intelligence organizations such as the CIA, MI-5, and MOSSAD.
Usually led by Nick Fury as executive director (although he reports to a twelve-member council, whose identities even he does not know), this organization often operates as much as a covert agency as a quasi-military one, initially depicted as affiliated with the United States government. Later, S.H.I.E.L.D. was depicted as under the jurisdiction of the United Nations, with vast technological resources at its disposal, with U.N. General Assembly Resolutions and legislation passed in signatory nations aiding many of their operations.
However, S.H.I.E.L.D. has been inconsistently portrayed as under U.S., rather than U.N., control, possibly by writers unaware of the agency's fictional history. For instance, in Astonishing X-Men #3, Nick Fury explains S.H.I.E.L.D.'s inaction during an incident of genocide by stating that it did not occur on American soil. --Wikipedia entry on SHIELD.
Within the Marvel Cinematic Universe, the SHIELD acronym stands for Strategic Homeland Intervention, Enforcement and Logistics Division.