I came across this earlier today. One of the most ingenious ways to use the internet to make practice time more effective.
Gary Willis, who is a renowned bassist has a great flash website that will test the limits of your reading ability.
Simply amazing. It will give you a random line of pitches and suggested rhythms. You can choose the frequency of sharps or flats and even use a predetermined range.
Make sure to pass this on to any of your students and friends!