These model agreement addenda and licenses provide language that authors can use to retain some or all of their rights when publishing or distributing their works. (Read about publisher agreements to see why this matters.)
Agreement to Extend Author's Rights (Boston Library Consortium) -- "Gives authors and their employing institutions non-exclusive rights to use, distribute, and reproduce material . . . in activities connected with the author's academic and professional activities."
Creative Commons license -- Allows you to retain the copyright to the work, yet also allow others to copy or distribute your work according to conditions you set. Some publishers will agree to publish your work under such licenses.