Physical and chemical properties are first reported in the primary chemical literature (i.e. journal articles and patent applications). Later, book editors and database providers compile the data into tables and charts so one can easily find multiple properties for a single compound. The UF Libraries have many print and online data compilations where you can find property information. Many of the resources on the recommendations page are also useful for finding property data.
Sigma-Alrich Website: Although Sigma-Aldrich is a commercial chemical supply company, their website offers a large amount of physical property and spectral data for commercially available products.