In late May 2003, I completed an exhaustive TI-BASIC tutorial covering the language for TI-83, TI-83+, and TI-83+SE calculators. Since then, the TI-84+ and TI-84+SE calculators have become available, and the guide covers almost all of their commands. This tutorial is meant for absolute beginners through moderately skilled programmers, assuming little or no experience in programming of any kind and only rudimentary math skills. For well over two and a half years, it has been available at ticalc.org; with the help of my compadre TI-Freak8x, it is now also available in online format. He worked out almost the entire conversion from PDF to HTML, and I fixed up a few things to make it compatible with the site template. You can find the link below; enjoy! I also recommend that you use it in conjunction with The BASIC Elite Guide.
View:
The Complete TI-83/+/SE/84+/SE BASIC Tutorials
--or at--
TI-Freakware