More information about the federal government's Rigs
to Reefs program is at www.bsee.gov/Exploration-and-Production/Decomissioning/Rigs-to-Reefs, with links to
state-specific programs in Texas, Alabama, Mississippi
and Louisiana (the link to California's program is currently
broken).
Other than contacting your state legislature, there are not
  many ways for divers to lend verbal or financial support for
  Rigs to Reefs. But the not-for-profit Coastal Conservation
  Association, with chapters in 17 coastal states, campaigns
  and seeks funding for the building of artificial reefs, including
  rig-to-reef projects. ( www.joincca.org/about )
Two researchers at the Scripps Institution of
  Oceanography started the Rigs-to-Reefs project, diving oil
  platforms off the California coast and in the Gulf of Mexico
  to document (with GoPro Hero 3+ cameras) the ecosystems
  that grow on and around the platforms, and using the
  information they gather to help the public make informed
  and responsible decisions about oil rigs in the ocean. You
  can see their photos and support their project at www.rig2reefexploration.org