Documentation about native programming on the TI CE calculators (84+CE / 83PCE)
Tutorials are located in the tutorials directory, and numbered in order of ability.
For more help, these links may be helpful:
Official eZ80 CPU documentation
Tutorials and information about eZ80 assembly (WIP)
TI-Planet's Project Builder, featuring an online CE C IDE
You can join this IRC channel and ask questions. Reponses may not be immediate, so please wait ~1 hour usually.