Links

What's this "GNU" All About, Eh?

GNU Project Home Page

FSF and GNU inquiries

Contacting the FSF

Official Stuff

TI-83 Plus Software Development Kit

This site by Texas Instruments gives you access to all the materials you need to create applications.

Download TI-83 Plus SDK Guide

Lots of highly useful information about the system architecture and how to create applications.

Download System Routine Documentation

A manual on all :/ the b_call()s.

Undocumented TI-83 Plus Features

A bunch of interesting stuff that TI did not go out of their way to provide. Stuff on undocumented system routines, monitor vectors, etc.

Z80 User's Manual

The official manual from those Intel renegades, ZiLog. Interesting, but not much to learn from. Apparently contains a lot of errors.
Download
Main Site

Various Forums and Sites

United-TI (Main site)
Detached Solutions (Main site)
Maxcoderz (Main site)
Greenfire Programming
TI Technology Discussion Groups (Main site)