This is a program I started making a while ago, although I never really got around to finishing it. I might later on, but I'm going to put it online for anybody to download it in case they want to finish it. It is in TI-BASIC for the TI-83+/TI-84+ series. It definitely isn't completely optimized at the moment, partially because I wanted readability. It is meant to serve as an aid to those learning about vectors because it offers (or it was intended to offer) a few handy features:
- Visual plotting (including addition and other operators) of 3-D vectors
- Conversion between equation formats
- A table of values for vectors
- The ability to calculate the angle between two vectors
- The ability to calculate where two vectors intersect
So far, all it can do is visually plot 3-D vectors, which is kind of cool, and adjust the window. Here's a screenshot of it:

It can be downloaded here:
http://bfr.tifreakware.net/VPLOT.8xp