This is a rhythm activity I do every year with K-3rd.
Each student gets:
1) A rhythm grid (provided in PPT),
2) a mini coffee filter (about $2 for 200 at Wal-Mart), and
3) ½ cup of fruit loops.
Instructions are included in the PPT. For younger grades copy rhythms with fruit loops, then clap and read the rhythms. For older grades start with copying, then progress to verbal dictation, and finally to aural dictation.