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.
Electronic Design Automation - Index is a system that can be used in the electronic world to keep track of your: Schematic, Printed Circuit Board, Front Plate, and Programmable Logic Unit numbers. This is very useful when you have drawn many electronic schematics and PCBs in an EDA program such as Eagle, gEDA, Protel, or Orcad. It's also useful if you've created a front plate layout in an image editor such as GIMP, Corel Draw, or Photoshop.