Ingredients:

Celery, cut into sections
Peanut butter (creamy works good but crunchy is fine too)
Raisins

Directions:

Make sure the celery is washed and dried off.  Spread peanut butter in the "valley" of each section.  It should resemble a small log.  Then add some raisins along the log like the ants are marching in a line.  I usually use the dark raisins since they look more like ants, but the light raisins are fine too, if you prefer.

You could also try these variations:

Cream cheese and dried currants 
Cream cheese and bits of black olives.
Or for the sweet tooth, you could try marshmallow cream and chocolate chips. 

Enjoy.

This makes a great afternoon snack that is healthy (except for maybe that 3rd variation LOL) and yummy too!