A database that contains dissertation citations back to 1861, abstracts back to 1980, and the full text of many dissertations from 1997 (and sometimes earlier) to present. Masters theses have been selectively indexed since 1962. Almost all dissertations written at UIUC from 1997 forward are available as a free full-text download in PDF (Adobe Acrobat) format. Here is an example of a subject search for education dissertations written at UIUC:
After performing your search and locating a dissertation of interest, you'll see a 'Full text-PDF' link at the right of the dissertation record if a full-text download is available. From there you can e-mail or export the citation and abstract. You also have the option of purchasing a copy by selecting the 'Order a copy' link.
If the full text is not available for download, a print copy of the dissertation may be available in the UIUC library--just do a search in the online catalog for the dissertation title to determine its location.
Abstracts for pre-1980 dissertations are available in Dissertation Abstracts, the print version of the database contents.
The University Library hosts a digital repository called IDEALS which contains recent dissertations (those which can be deposited digitally via word documents, etc) and working papers for Illinois faculty and doctoral students. Advantages are retaining your own copyright and having it be discovered more quickly via OpenSource.