As of August 1, 2012 Rackham Graduate School no longer requires doctoral students to submit their dissertations to UMI Dissertation Publishing (a division of ProQuest). UMI has been publishing theses and dissertations for over half a century, and many graduate students publish with UMI. Rackham has more information on dissertations here: Submitting the Dissertation.
If you choose to publish your dissertation with UMI, you will sign an agreement form granting ProQuest/UMI a non-exclusive license to duplicate and distribute your thesis and to publish the abstract that you prepare. You retain the copyright in your thesis, and you keep the right to publish your thesis elsewhere, in book form or as separate articles. ProQuest/UMI takes care of the arrangements for (a) publishing the abstract in Dissertation Abstracts International; (b) preparing a microfilm copy of the dissertation; and (c) depositing microfilm copies in the University Graduate Library.
You can make your thesis freely available by depositing it in Deep Blue, U-M's institutional repository. It will be part of Deep Blue's growing collection of dissertations from the University of Michigan, and will appear in search results from Google and Google Scholar.
UMI offers an Open Access Option for an additional fee, in which ProQuest/UMI makes digital copies of your thesis available as a free download. However, both Rackham and the University Library recommend that you choose the Traditional Publishing Option, and use Deep Blue to make your dissertation freely available online.
To deposit your dissertation in Deep Blue, contact Rackham's Office of Academic Records and Dissertations or call 734-763-0171.
ProQuest/UMI offers a service in which they will register your copyright for you, and deposit the required copies with the Copyright Office. The fee for this service is $65, which includes the $35 copyright office fee. Although registration is not required to preserve your copyright, most copyright specialists feel that it is advisable since registration offers certain legal benefits if someone infringes on your copyright and you wish to bring suit. Note that if you choose not to register your copyright through ProQuest/UMI, you can still register it on your own, either at the time you deposit your thesis or at some later date. Information on self-registering your copyright can be found at eCO:Electronic Copyright Office.
For more information about the University of Michigan's dissertation requirements, see Rackham's dissertation handbook.
For more information about publishing with ProQuest/UMI, visit ProQuest/UMI.
For a detailed explanation of copyright law as it relates to graduate research, see Copyright Law and Graduate Research: New Media, New Rights, and Your New Dissertation, by Kenneth Crews. (link broken - perhaps ProQuest has posted it elsewhere?)