IMathAS (Internet Mathematics Assessment System) is a Web-based math testing and homework system. It is a light course/learning management system and testing system, similar to and inspired by WebWork and WIMS, and similar to textbook-bundled systems like iLrn and MathXL. It requires a browser with MathML and SVG support such as Firefox 1.5 or IE6 with plugins.
polygon is a set of PHP classes that can be used to perform different types of geometric operations with arbitary polygons. It provides generic polygon and vertex classes that support mixing lines and arc segments between vertices. Polygons may be self-intersecting, convex, or concave. It provides means to perform intersection and union operations with the shapes and to compute shape clipping.
Electronic Engineering Tool is a Web-based tool that includes an electronic formula calculator and converter functions. It very useful when working with electronics, both for engineers and amateurs. For example, it includes converters for dBm-to-Watt and Fahrenheit-to-Celsius, and it can calculate Ohm's law, filters, thermal resistant C/W, SWR, coil inductance, capacitor capacity, and more.