The recently launched Readium Foundation is doing some great work on EPUB 3 with both Readium SDK (native code renderer for Android, iOS, OS X and Windows) and Readium.js (JS based).
Among the other projects that this open source foundation could focus on, I made a proposal to build and open source OPDS libraries in both JS and native code for mobile platforms.
Several companies involved in Readium have directly expressed their interest (that's the case of Benetech, Bokbasen and Feedbooks) and several more are also using OPDS in their projects (Bluefire, Aldiko, Mantano and Izneo).
A much needed improvement to the Wikipedia page
has also been rolled out and I'll continue to improve it in the upcoming months.