Bring back the spirit of the '60s with a DIY lava lamp. Remove the label from an old soda bottle or other clear plastic container. Fill a quarter of the bottle with water, and then add vegetable oil up to the halfway mark. Add 10 to 12 drops of food coloring before breaking an Alka-Seltzer tablet into six pieces and dropping them into the mixture. To complete the effect, go into a dark room and shine a flashlight through the bottom of the bottle. Groovy!