Thanks to pinterest, I discovered another useful resource today for practicing rhythmic dictation skills during piano lab. At http://www.therhythmtrainer.com/ . I like how there are options for fast and slow speed. You can also customize what combination of note values to practice with including different combinations of eighth and sixteenth notes and rests.
Another useful feature is the 2 mode options. For mode A, students listen to a one measure rhythm pattern (in 4/4 Time) and then construct it by clicking on rhythm values in the correct order. In Mode B you can see the rhythm pattern and then select from multiple choice audio samples to select the pattern that matches the rhythm that you see. This will definitely be added to my link list of online piano lab activities.