I have compiled a list of sources for the elements that are available to the amateur chemist. Sodium will be discussed here.
Sodium is a light, low-melting, reactive metal. It belongs in the alkali metals group. It oxidizes rapidly in air, and its reaction with water is famous. It is one of the most widespread metals in the form of its compounds. Sodium chloride is the most well-known sodium compound. Sodium metal has a few specialized uses, such as a coolant in some nuclear power plants.
In element form: Low pressure sodium vapor lamps have pure sodium metal in them. High pressure sodium lamps have sodium amalgam in them.
In compound form: Sodium chloride is the most common sodium compound. Baking soda also contains sodium, as do many other chemicals.
Here is my sample of sodium in the form of one of its compounds, sodium bromide.