Coffee , tea and chocolate all naturally contain varying amounts of caffeine , while colas often have different amounts of caffeine added to them.

Caffeine in Tea
There are many factors influencing caffeine levels in tea , including brewing time / temperature, tea grade and tea varietal.
Tisanes or "herbal teas" (including many of Celestial Seasonings' "teas") are usually caffeine free. Similarly,teas blended with other ingredients (such as mint green teas or masala chais ) will often have lower caffeine levels than unblended teas.
Most studies show that black tea has between 40 and 120 mg caffeine per eight ounce serving. Decaf black tea usually contains about two to ten mg of caffeine.

Caffeine in Colas & Sodas
The caffeine levels listed below are for eight-ounce servings. They are in declining order.
*. Pepsi Max/Diet Pepsi Max - 69 mg
*. Mr. Pibb / Sunkist Orange - 40 mg
*. Wild Cherry Pepsi - 38 mg
*. Pepsi-Cola /Pepsi Twist/SietPepsi Jazz - 37.5 mg
*. Pepsi One / Mountain Dew / Mountain Dew Code Red / Diet Mountain Dew - 37 mg
*. Diet Pepsi - 36 mg
*. CocaCola Zero / Mello Yello - 35 mg
*. CocaCola Classic /Cherry Coke/Lemon Coke/Vanilla Coke - 34 mg
*. Tab - 31.2 mg
*. Diet Coke - 30.4 mg
*. A&W Creme Soda - 29 mg
*. Dr. Pepper / Diet Dr. Pepper - 27 mg
*. Barq's Root Beer - 23 mg
*. Mugg Root Beer / 7-Up / Sprite / Fresca / Fanta (all flavors) / Slice / Sierra Mist- 0 mg

Caffeine in Chocolate
*. Slim-Fast Chocolate Beverages (1 serving) - 20mg
*. Dark Chocolate (1 oz) - 20 mg
*. Milk Chocolate (1 oz) - 6 mg
*. Chocolate Milk (8 oz) - 4 mg
*. White Chocolate (1 oz) - 0 mg