Quizzley is a simple site that allows you to create a quiz or a poll and distribute it to your audience. Once your audience pairs with the quiz/poll, their smartphone will automatically transform into the voting pad. It's a fast way to interact with your audience; no authentication or registration are needed.
garith is a game similar in spirit to BSD's "arithmetic" or TuxMath. The game asks you to perform a simple arithmetic operation within a certain time frame. It improves your skills by stressing the operations you get more frequently wrong or that longer to answer. The statistics are saved/restored across games, so that each game is tuned for your current arithmetic abilities.