I have compiled a list of sources for the elements that are available to the amateur chemist. Carbon will be discussed here.
Carbon has several physical forms, or allotropes. Graphite is black, soft, electrically conductive solid. Diamond is a clear, hard, electrically insulating solid. There are other forms like carbon nanotubes and fullerenes that are interesting but too expensive for such a common element. Graphite is used in pencils and carbon-zinc batteries. Diamonds are used as abrasives and jewelry.
In element form: Obtain graphite from an art supply store. Buy an artificial diamond. Open a carbon-zinc cell and remove the carbon rod. Use the impure carbon in a pencil lead.
In compound form: All organic compounds contain carbon.
Here is my sample of carbon. It is composed of graphite rods from a carbon-zinc cell.