Wikipedia: Cannabis Foods

Cannabis foods concerns the preparation and cooking of foods with the drug cannabis in herbal or resin form as an alternate way to experience the effects of the drug without smoking it. Commonly it is cooked into a cake, cookie, brownie, or other baked product to be distributed socially. There are many different names and slang terms for these recipes. Most are based on standard recipes for brownies, cakes or cookies. Often, prefixes such as hash, cannabis, weed, pot, space, cosmic, magic, special, enhanced are added to the name of the food that they are prepared with: "hash cakes," "special brownies" etc.
Tetrahydrocannabinol is insoluble cold in water, but soluble in oil or alcohol.

Tetrahydrocannabinol (THC), the active substance in cannabis, and other cannabinoids are hydrophobic oils, which are insoluble in water but soluble in lipids (oil/fat) and alcohol. Thus, using either one of these to extract THC from cannabis is required to have the cooked product be psychoactive.[1] Furthermore, during preparation, the cannabis or its extract must be sufficiently heated or dehydrated to cause decarboxylation of its most abundant cannabinoid, tetrahydrocannabinolic acid, into psychoactive THC.[2]

The oil-solubility of cannabis extracts has been known since ancient times, when Sanskrit recipes from India required that the cannabis (ganja) be sautéed in ghee before mixing it with other ingredients.[1][3] Making a tea by boiling cannabis in water is a highly inefficient way to extract cannabinoids, although if the cannabis is of good quality and has plenty of resin on the outside, a portion of resin can be softened by the heat and float out into the water. (THC is fat soluble and needs more than just water to have a proper effect).

Some authors claim that oral consumption of cannabis, when properly cooked, is a more efficient way to absorb cannabinoids than smoking it.[4]

"Cannaoil" or "marijuana oil" is a cooking oil based product that has been infused with cannabinoids. This can be achieved by cooking the oil at an extremely low temperature along with ground cannabis for a long period of time to allow the cannabinoids to absorb into the fat within the oils. This can be as easy as using a frying pan or pot, or using a double boiler, or the easiest method using a crock pot. Cannaoil can be used in any recipe that calls for oil that does not go above the temperature at which THC vaporizes, which is 210 degrees Celsius.

Butter

"Cannabutter" or "marijuana butter" is a butter-based emulsion which has been infused with cannabinoids. This is achieved by heating the raw cannabis along with butter and allowing the cannabinoids to be extracted by the fat. The equipment necessary for the manufacture of cannabutter can be as simple as a sauce pan and spatula or as complicated as a double-boiler, or crock pot, cheese cloth or tea strainer and funnel.[5]

Liqueurs

Because cannabis resins are soluble in alcohol, an effective way of adding them into dishes is through cooking brandy or rum infused with cannabinoids.

Creme de Gras is a flavored liqueur made from cannabis.[6] It can be added to coffee and other beverages.

Source: http://en.wikipedia.org/wiki/Cannabis_brownie
Wikipedia: Cannabis foods