1 bottle (4 oz) plain school glue
1/2 teaspoon Borax (sold on the laundry aisle)
Empty the glue into a bowl. Fill empty bottle about halfway with warm water. Replace cap and shake to rinse bottle of glue. Pour into glue. Stir to combine. Add several drops of food coloring at this point. In a separate container mix about 1/4 cup of water with the Borax. Stir to dissolve Borax. While stirring glue mixture, slowly pour Borax into glue. Almost immediately you will feel the consistency change. I had to abandon the spoon and finish mixing with my hands. I usually had a little water left that didn't mix with the slime. The more the slime is played with the stiffer it becomes.
We have had a lot of fun with it. We let it drip over the sides of a cup and it slowly oozes down the sides and puddles on the counter. The kids really had a ball with it!