Web Elements
Web Elements Periodic Table: Osmium
This WebElements site offers lots of fundamental information on osmium, Bohr diagrams and details on its purification.
Corrosion Source
Corrosion Source: Osmium
This resource presents basic data, along with good information on the history, sources, properties and uses of osmium.
Chemicool
Chemicool: Osmium
This site, which is provided for by Chemicool, gives a set of data tables that cover a great many physical and chemical properties of osmium.