Ubuntu SDK Apps Collection is an interesting official project that gathers Ubuntu SDK-based third-party applications, in order to land them by default in the Ubuntu Touch installable images, thus making them available for testing to a wide audience.
Ubuntu SDK Apps Collection groups apps into a dedicated PPA, where captivating games and useful apps have already started to land, software including Akari, Dogfight, Electronics Toolbox, Mastermind, Samegame, Stock Ticker Mobile app, Sudoku Touch, LightOff, uReadIt, XKCD Viewer.