The Endocrine Society - who publish titles such as the Journal of Clinical Endocrinology and Metabolism and Endocrinology - have developed an open access option for Wellcome Trust funded authors.
"The Endocrine Society will offer authors supported by the Wellcome Trust the option of meeting the publication requirements of the Trust by paying for an open access option. The cost to authors would be $3,000. Upon receipt of payment, the final print version will be deposited in PMC for immediate open access. These articles will be licensed using the Creative Commons, Attribution, Non-commercial license 2.0. " Further information is available from the Instruction to Author's page.
Currently this option is only available to Wellcome Trust funded researchers.