Po-Shen Loh at Carnegie-Mellon is perhaps best known for his success coaching the US Math Olympiad team. However, he is equally passionate about a project he started called Expii that he hopes will provide self-directed learning of mathematics using open-source contributions and a sophisticated dynamic learning system.
Mathematical subject matter is organized in a collection of nodes that are determined by a core group of editors at Expii. Navigating through the nodes eventually leads to a specific topic node. Within that topic node resides a collection of explanations and exercises for that specific topic written by a volunteer contributor. Explanations are constructed on the site's easy to use editor which recognizes LaTeX. The site also allows one to embed instructional YouTube videos. Exercises too are easily constructed within the site's builtin editor.
There are two aspects to Expii that separate it from other open source on-line learning systems, the editorial approach and the dynamic learning algorithm.
First, unlike the Wikipedia editorial approach, contributors do not typically edit other contributors' work. Factual corrections to an existing contribution are welcome, but stylistic re-writes are discouraged. Rather, if a contributor does not like the style of a particular explanation, that contributor is encouraged to submit a competing explanation in the style that they prefer. Subsequently, the two (or more) explanations then compete with each other by receiving upvotes/downvotes from users of the site. Explanations with more votes are listed first when a learner visits a particular node. Prof. Loh hopes that this approach will provided a variety of explanations on different topics that will resonate with different learners.
Second, the learning algorithm is a novel application of the ELO ranking system that is used in international chess competition. In a sense, learners and exercises are in competition with each other and are ranked using an ELO-type system. In this way, when a learner requests an exercise on a particular topic, their ranking is matched to an exercise with a nearby ranking. As the learner improves, their ranking improves and they are presented with increasingly challenging exercises.
At the moment, the Expii effort is funded by private investors and is a for-profit entity. However, Prof. Loh says that the future business model will not include a paywall for access to the site. Rather, one possible business model would be mediating the pairing of contributors and learners on Expii into paid, adhoc, teaching and tutoring relationships. The core group is looking for investors and applying for federal grant money to keep the 3-year effort going. There has been steady growth in both users and contributors, but it seems to not have reached "critical mass" yet.
The site welcomes the addition of existing open-source materials as long as they are appropriately licensed. For example, a Creative Commons license that allows commercial use would work.
Prof. Loh states that a lot of his motivation for starting the site came from his work with the Math Olympiad and other mathematics competitions. He recognizes that for the US (and other countries) to compete, there needs to be a large pool of talented mathematics students. He hopes that Expii can deepen that pool. Indeed, he hopes that it can take a struggling mathematics student that may not be getting quite what he/she needs in their home classroom and provide just the right kind of learning experience to turn them into future Math Olympians. And, as a great side benefit, Expii will elevate the mathematical literacy across the board.
If you have OERs that you have developed and would like a venue, Expii may be a good choice for you. The ranking system may be the kind of objective assessment of your work that could be used in tenure, promotion and merit considerations at your institution.