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Although Texas Instruments (TI) is the most widely recognized calculator company and its calculators are the most widely used and supported, there are other calculator companies that produce their own suite of calculators, most notably Casio, Hewlett Packard (HP), and Sharp. Casio was actually the first company that produced a graphing calculator (the fx-7000G), and its calculators provide much of the same functionality and capabilities as the TI calculators such as graphing, complex math, and built-in programming.
Just like with the TI community, there is a sizable user community around the Casio calculators. The most notable Casio sites are casiopeia, casiocalc, and planete-casio. Some of the TI community sites also provide support for Casio calculators, acting as a bridge that unites the TI and Casio communities together. In particular, Omnimaga, CodeWalrus, Cemetech, and TI-Planet.