I was in a corporate library originally. They do hirer much quicker, but there are less opportunities and often jobs are not as secure long-term.
Cover letters and resumes are no different for special libraries. You just use the same terminology as represented in the job ad for skills and requirements. This should be what you do for every job you apply for anyways, no matter the type.
Brian C. Gray
Head of Reference & Engineering Librarian
Kelvin Smith Library
Case Western Reserve University
http://blog.case.edu/bcg8bcg8@case.edu