This Topic in Depth explores the Web's offerings on the physics of fluids. By an educational Web site called School for Champions, the first site is the Fluids lesson plan (1). Here, students or anyone interested can read about the basics of fluids and then take a short interactive quiz on the topic. The second site is maintained by Steve Lower of the Department of Chemistry at Simon Fraser University called Liquids and their Vapors (2). This Adobe Acrobat (.pdf) file contains an eighteen-page document that covers topics such as properties of liquids and changes of state. The next site contains an interactive multimedia activity presented by explorescience.com called Floating Log (3). The site allows users to explore how a fluid can affect buoyancy by letting them change the mass of the log and the fluid's density. The next site from Purdue University's Chemical Education Web site is called Liquids (4). This page describes the structure of liquids, what kinds of materials form liquids, vapor pressure, and more. The fifth site, offered by Professor M.S. Cramer at the College of Engineering at Virginia Tech, is entitled Gallery of Fluid Dynamics (5). It contains movies, animations, photographs, and descriptions of various fluid mechanics topics such as condensation, shock waves, and supersonic cars. Next comes the Innovative Technology Solutions Corporation's Fundamental Fluid Mechanics Movies Web site (6). Over thirty short films show how fluids move in various conditions including gravity waves, fire, material transport, and hydraulics. From the University of Waterloo's Department of Mechanical Engineering-Microelectronics Heat Transfer Laboratory comes the next site, called the Fluid Properties Calculator (7). This online tool allows users to select a fluid and enter a temperature to calculate various parameters such as density, viscosity, specific heat, and thermal diffusivity. The last site is the online journal Physics of Fluids (8), which is published monthly by the American Institute of Physics with the cooperation of The American Physical Society Division of Fluid Dynamics. The journal is "devoted to the publication of original theoretical, computational, and experimental contributions to the dynamics of gases, liquids, and complex or multiphase fluids" and provides free full-text articles for online viewing.