I have compiled a list of sources for the elements that are available to the amateur chemist. Nitrogen will be discussed here.
Nitrogen is a colorless, odorless, tasteless, relatively inert gas. It reacts directly and easily with very few elements, lithium being the only metal that reacts with nitrogen at room temperature. Some other metals form nitrides when they burn in air, such as magnesium. Nitrogen forms a wide array of compounds. Ammonia is used in cleaning. All proteins contain amino acids, which contain nitrogen. Hydrazine is used as a rocket fuel. Sodium azide is used in airbags. Nitrous oxide is used in canned whipped cream. Nitrites are used to preserve food. Nitrates are used as oxidizers in pyrotechnics. Most explosives contain nitrogen compounds.
In element form: Heat ammonium dichromate. The corrosion of a metal in a test tube inverted in water consumes the oxygen, leaving mostly nitrogen behind.
In compound form: Nitrates are common fertilizers. Ammonia is one of the most common nitrogen compounds.
Here is my sample of nitrogen gas. It was created by the corrosion of steel wool in a test tube, absorbing oxygen and leaving 95% nitrogen behind.