University libraries are particularly noted for special collections of government documents, microfilm, microfiche, rare books or manuscripts. Some universities have an archives housed separately from the general library. Here's a sampling of microform collections especially interesting to family historians:
American Culture Series, 1493-1875 (University Microfilms): publications on all aspects of American life. Here you'd find, for example, History of the Old Cheraws, about South Carolina, 1730-1810, originally published in 1867. The American Farrier and Family Medical Companion, published in 1852, gives advice on popular medical remedies.
Confederate Imprints (Research Publications): official and unofficial publications of the Confederacy. It contains such items as the organization of the army, instructions for mail carriers, hymn books and sheet music.
History of Women (Research Publications): publications by and about women up to about 1920. An Essay on the Education and Genius of the Female Sex (1795) and The Good Housekeeper (1839) are just two examples.
Western Americana (Xerox University Microfilms): publications about and contemporary with each successive frontier. The Navigator: Containing Directions for Navigating the Monongahela, Allegheny, Ohio and Mississippi Rivers..., published in 1814, was a guide for travelers. Miners and Business Men's Directory for the Year Commencing January 1st, 1856 could help trace a participant in the gold rush.
Special collections often aren't indexed in the library's catalog. Be sure to ask a reference librarian about any special holdings that may aid your research.