CHEMnetBASE is an informational Web site provided by the chemical reference publisher Chapman & Hall / CRC. Although some resources on the site are for subscribers only, the Handbook of Chemistry and Physics is available to anyone. The Handbook contains a wealth of helpful information for researchers ranging from Constants and Units to Thermochemistry and Kinetics. These and many more subjects can be browsed using the table of constants (opening the links in a new window helps avoid the small frame size) or can be searched by substance and property or by general text.