A lot of teachers are lucky enough to have a laptop and projector set up in the classroom and with an internet connection too.
Heads up! Roadtogrammar.com is perfect for use with a projector! Project the quizzes onto the screen and go over the questions and answers with the entire class. I do it all the time and it really gets the students focussed.
Since almost every grammar topic is covered on roadtogrammar.com, it's a great resource that you can use anytime.