The best resource for current test materials for common graduate school and licensing exams is the Testing and Education Reference Center Database. It includes study guides, practice tests, and other materials for the GRE, GMAT, LSAT, and other common tests. This database also has "Career Tools," including a Virtual Career Library and a resume builder.
You can also search in QuickSearch to locate more print and electronic books in these areas. For example, try searching for the name of a test or use the general search term "examination study guides."