KnightOS is an open-source operating system for TI calculators. It completely replaces the stock TI-OS, and offers loads of great features for programmers and users alike:
Easy-to-use graphical interface
Runs several programs at once
Extensible with third party libraries
KnightOS supports the TI-73, TI-83+, TI-83+ Silver Edition, TI-84+, TI-84+ Silver Edition, TI-84+ Color Silver Edition, and the French variations on these devices.
KnightOS could always use some help from programmers and non-programmers alike. If you're a coder, you'll love working with the codebase and building neat things. If you aren't, you can still help out by helping us write documentation, spreading the word, or by simply hanging out with us to offer your thoughts on what you want KnightOS to be. Come join us on IRC to get to know us and share your thoughts. We do have to sleep sometimes, so be patient. We may not be around when you arrive, so say "hello" and sit tight for a while.
We're also interested in calculator donations. If you can spare one, please get in touch on IRC and we'll work it out.
If you're a user, you may want to wait. KnightOS is not done yet, and isn't ready for general use. However, if you're a programmer, you can dive in and start hacking on it right now. The same does apply to you, though: it's not done, so expect a little difficulty. To get started writing code for KnightOS, head over to the documentation. You are strongly encouraged to hang out in the IRC channel, where your questions can be answered and you can learn more about the project.