I use flashcards to practice rhythms in my classroom all the time! They are great for whole class instruction/practice, and they are wonderful to use in small groups for extra practice. This set includes 18 different 4 beat rhythm patterns, and uses quarter notes, paired eighth notes, and quarter rests in stick notation.
Simply print, cut in half, and laminate, and you'll have a great collection of flash cards (that you didn't even have to break out the markers to make)! I like to print mine on bright card stock, so they really stand out.