A repository can be an important element of a collaborative learning environment. For example, the environment we are developing for (and with) honours students in research psychology revolves around students creating research reports to be added to a repository. Some of the reports in the repositories are later included in Unisa Psychologia - an 'overlay journal' that foregrounds some of the best and most interesting work. Similarly, the University of California's eScholarship Repository (also see this The Scientist article about it) is intended as the back-end for a series of overlay journals.
In other cases, participants in a collaborative environment may need to draw on learning objects to gain skills in performing particular tasks.
The Scholarly Publishing and Academic Resources Coalition (SPARC) has a useful resource page listing active institutional repositories and sources of information about institutional repositories. They also have a page on software tools for repositories and online journals.
The Budapest Open Access Initiative has a short comparative guide to open-source institutional repository software which includes a comparative table. In addition to Eprints and Dspace, they also cover CDSware, i-Tor and MyCoRe. The comparison unfortunately does not provide simple, clear summary conclusions on which system is best for which kind of user, but there is detailed information on how the systems differ. For example, the Dutch i-Tor system seems to be a good choice where institutions don't want to keep content in a separate repository system, but would rather superimpose a repository layer on top of their current diverse databases. All the systems reviewed are Open Archives Initiative compliant.
through automation (intelligent tutor systems selecting and sequencing objects)
by hand (course designers selecting and sequencing objects - perhaps using design tools such as Instructional Architect)
by community (i.e., collaborative learning where participants both produce and use learning objects).
Merlot is a repository of online learning materials
What are repositories for?
Conventionally, repositories are about preserving things and making them available for re-use. So the obvious use of repositories (of, for example, learning objects) is for lecturers to draw learning objects from the repository and to fit them together like lego bits to make courses. When students then do these courses the learning objects are 'played out' in the sequence determined by the lecturer. However, in a less linear and more collaborative learning environment, students use the objects more actively to build their own knowledge products. What students and lecturers learn (and practice and invent) in the process is what Stephen Downes calls the new literacy or hyper-grammar of the information age - just as they traditionally did with the grammar of conventional linear texts such as essays. This new literacy ("students use hyper-grammer... their attention is polyfocal, and... their interactions are multi-threaded") can be used and explored and developed and is not in principle worse than traditional linear literacy. Thus at least one use for repositories is in an environment where lecturers and students operate as knowledge bricoleurs.