In their article on learning objects as tools for teaching information literacy, Mestre et al. broadly define a learning object as "a reusable instructional resource, usually digital and Web-based, developed to support learning." They go on to identify types of learning objects, including "instructional modules, tutorials, instructional games, blog, research guides, narrated PowerPoint presentation, podcasts, photos, images, quizzes, surveys, tutorials, and videos."
A learning object repository is an online library for storing, managing, and sharing learning objects. The repositories in this list contain material that has been submitted by librarians and subject discipline faculty and,reviewed (in many cases peer-reviewed) for quality.
This is a selection of smaller repositories from individual universities. Some of the individual tutorials or modules may also appear in Merlot or PRIMO. However, PRIMO is relatively selective (and thus small), while Merlot has information literacy/library learning objects mixed in with all of the other subjects/disciplines. Also, it can be helpful to look at a library's learning object collection in its entirety for context. For those reasons, you might want to browse through some of the university collections before tackling the larger respositories.
The ACRL Instruction Section's information literacy listserv, ILI-L, is a good place to identify recommended learning objects used by other librarians. If you are a list subscriber, you can go to the List Home, login and search the Archives.