Academic publishers sometimes require authors to turn over copyright in their works to the publisher. Faculty are often surprised to discover that they may no longer own the copyright to their works. Academic authors have various tools to negotiate with publishers to retain the rights they may need after their work is published. For example, a faculty member may want to post his or her article on their departmental or personal website for everyone to download free of charge. If the faculty member signed away that right, he or she would be in violation of their publishing contract. Thus, The CIC Provosts have approved an authors addendum  (pdf), which can be attached to a publication agreement for a faculty member to negotiate for retaining specific rights. Alternatively, an faculty member may choose more author-rights friendly publishers. The Sherpa-Romeo database  allows searching for publisher copyright policies. For more information about authors rights, visit the Association of Research Libraries' SPARC Resources for Authors  site.
Finally, if you have created a work and you would like to encourage others to use it and share it, the Creative Commons  project may be of interest. Creative Commons licenses allow a creator to simply identify the types of uses that are allowed and those that are prohibited. For example, the Creative Commons Attribution-Noncommercial-Share Alike license  allows others to freely reuse the work for noncommercial purposes, and to create derivative works as long as they are also shared under the same terms.
For an expanded discussion of these issues, consult the libguide on Scholarly Communication , published by Northwestern's Center for Scholarly Communication and Digital Curation .