Some of you may have already seen this, but here's my chemical equation solver. I think the redeeming aspect of it is that it takes string input and parses it instead of asking a billion questions about how many products or reactants or elements you have. Plus, it's only 928 bytes!
Here it is.
Well, I've pretty much finished this, but I suspect that I haven't optimized this fully (for speed). The program took six ticks on a SE to solve the equation on the bottom-left in the screenshot. On a 83+ I imagine it'd take 15 ticks, crazy! Could anyone skilled with TI-BASIC take a look and see if there's anything left I can do to make it go a little faster?