Before the ground is covered with snow, and your acorns are lost until Spring, gather up a few and make some colorful versions using pretty embroider floss.
You'll need about one skein of thread per acorn. I love the rainbow of hues embroidery thread comes in -- I usually get DMC Cotton Embroidery Floss, which they sell at Michael's and other craft stores for about 39 cents! All you have to do is wind the thread into a ball, as if it were a tiny ball of yarn.
Now just pop off an acorn cap (use a craft knife, such as an X-acto knife, to separate the cap from the body if need be.) Add a dab of hot glue to the ball at the thread's end, then attach the cap. Squeeze the ball with your fingers to create an "acorn" shape.
These make cute present toppers and ornaments, or fill a small bowl with them to add a splash of color to a dresser or coffee table.