Had not heard about CITIDEL (Computing and Information Technology Interactive Digital Educational Library) before. This seems to be quite a serious effort: they claim 488242 entries!
Among the things I like:
- Resources (the word “learning object” seems to be avoided) are classified in a number of schemes: ACM/IEEE Computing Curricula, ACM Computing Classification System, Computing Research Repository (CoRR) Subject Areas and AMS Mathematics Subject Classification. I assume that the schemes are interlinked, so that a classifying a resource in one of them automatically makes it available in the other ones at the equivalent location?
- CITIDEL includes resources from for instance the DBLP Computer Science Bibliography: it seems like they harvest through OAI external collections.
- CITIVIZ is a tool that provides access to CITIDEL through information visualization techniques, not unlike our work in ARIADNE.