Calcium is found in foods such as dairy products, dark-green leafy vegetables, sea vegetables, canned salmon, sardines, tofu and sesame seeds. There is twice as much calcium in a cup of spinach as in a cup of milk. Supplementation:

Inorganic calcium forms (calcium sulfate, calcium phosphate and calcium carbonate) are poorly absorbed. Organic forms have better absorption rates which can run anywhere from 25% to as high as 95%.

Calcium orotate (90 to 95% absorbed) is the best, closely followed by calcium aspartate (85% absorbed). However, these are not only the most expensive, but they're also the harder to find. That means they may not be an option for many people.

Another good one is calcium ascorbate, which also provides vitamin C as the other part of the molecule, along with the fact that it's no longer an acidic form of vitamin C.

The amino acid chelates (65-80% absorption) are still fairly expensive, and not as easily found (though easier than the preceding two). These are probably the best compromise if you're willing to spend just a bit more.

The best compromise of price, percentage of elemental calcium, and absorption would probably be calcium citrate. The absorption is 30 to 35%, and the citric acid reduces the amount of stomach acids required for absorption. For most people, calcium citrate would be the most reasonable choice.

Calcium content of foods (mg per 100gm / 3.5oz portion):

Human Breast Milk	33 (low!)	Almonds	234	Amaranth	267
Apricots (dried)	67	Artichokes	51	Beans (can: pinto, black)	135
Beet greens (cooked)	99	Blackeye peas	55	Bran	70
Broccoli (raw)	48	Brussel Sprouts	36	Buckwheat	114
Cabbage (raw)	49	Carrot (raw)	37	Cashew nuts	38
Cauliflower (cooked)	42	Swiss Chard (raw)	88	Chickpeas (garbanzos)	150
Collards (raw leaves)	250	Cress (raw)	81	Dandelion greens	187
Endive	81	Escarole	81	Figs (dried)	126
Filberts (Hazelnuts)	209	Kale (raw leaves)	249	Kale (cooked leaves)	187
Leeks	52	Lettuce (light green)	35	Lettuce (dark green)	68
Molasses (dark-213 cal.)	684	Mustard Green (raw)	183	Mustard Green (cooked)	138
Okra (raw or cooked)	92	Olives	61	Orange (Florida)	43
Parsley	203	Peanuts (roasted & salted)	74	Peas (boiled)	56
Pistachio nuts	131	Potato Chips	40	Raisins	62
Rhubarb (cooked)	78	Sauerkraut	36	Sesame Seeds	1160
Squash (Butternut)	40	Soybeans	60	Sugar (Brown)	85
Spinach (raw)	128	Tofu	93	Sunflower seeds	120
Sweet Potatoes (baked)	40	Turnips (cooked)	35	Turnip Greens (raw)	246
Turnip Greens (boiled)	184	Water Cress	151

Don't forget, the right water can contribute to your daily calcium intake too. Consumption of mineral-rich water contributed up to 25% of daily calcium and 17% of daily magnesium intake in a French population study. [J Am Diet Assoc 2002;102(11): pp.1658-62]