The UK Pony Club has just launched a new 'Pony Prep' website:
While it is quite obviously aimed at the younger set, it nonetheless has some good instructional videos and simple quizzes you can take to test your knowledge: especially useful for those assessing Horsemanship level 1 on the 27th. You don't need to log in or create an account to take quizzes and view the videos like this one:
Bear in mind the British terminology sometimes differs from our own (we say 'halter' for 'headcollar'), but this site will match nicely with the Manual of Horsemanship.
The Canadian Pony Club also has a games page:
The quiz questions are more difficult (and sometimes quite obscure), but the points of the horse page is useful.
Have fun, and feel free to post your high scores in the comments section of this page!