I have compiled a list of sources for the elements that are available to the amateur chemist. Selenium will be discussed here.
Selenium, like most nonmetals, is quite a unique and interesting element. Selenium is necessary in small quantities in the human body, but toxic in larger amounts. The element itself has three forms: a glassy, black, nonmetallic form; a red, powdery, nonmetallic form; and a gray, malleable, semimetallic form. This gray form is the most useful and the most common form of selenium. Selenium has the interesting property of changing its conductivity upon exposure to light. Therefore, it was used in the first photodetectors (cadmium sulfide is used now). Selenium forms a highly toxic and smelly dioxide which is the primary selenium compound. Selenium forms binary molecular compounds as well as anionic covalent complexes like selenite and selenate. Selenides replace a small amount of sulfide in many ores, making selenium a common byproduct in processes like copper production.
In element form: Selenium rectifiers contain a thin layer of selenium metal, as well as old photocopier machines and light meters.
In compound form: Selenium sulfide is used in Selsun Blue shampoo. Organic selenium complexes, as well as the inorganic selenites and selenates, are both used in selenium vitamin supplements. Selenium toners contain sodium selenite.
I do not have any verifiable elemental selenium. I do have a few specks that precipitated out when some selenium vitamin supplement slurry was electrolyzed, but of course they are not selenium. I plan to purchase pure elemental selenium in the near future, after which this page will be updated.