As you've probably guessed by now, I am a proud owner of a TI 83 which I affectionately call 'Chuck the Math Monkey'. If you too are a proud owner of one of TI grapher and are trying to learn how to use it, then you've come to the right place. Perhaps you're only considering buying one. Here are a few things to consider:
You may not need a graphing calculator. They are not necessary until beyond Alegbra 2 but can be very helpful. I myself made it all the way through Physics with nothing but my trusty TI 25 - the cheapest Scientific calculator. Personally, I recommend waiting until Geometry or later before getting a grapher, unless you want games or you're a geek like me who likes having a pocket computer. :]
Which brings up another good point: the different kind of calculators. You have Scientific, which are useful in low to mid level math courses and everyday usage, and then you have Graphing calculators. The graphers are actually split in two groups: those with QWERTY keyboards and those with the traditional number pad. QWERTY keyboards are like what you use with a computer and get their name from the position of the keys (the top left starts with 'q', then 'w'...). You won't see these much at all in High School because that fact they only appear on the TI 92 or higher, which happen to be banned from the SAT. High School academics almost always adopts the SAT standard.
You're probably more familar with the number pad graphers: TI 82, 83, 83plus, 85, 86, 89. Don't let the numbers fool you though, they don't go in order! The 82 and 85 are similar in capablities. They differ in slightly different interfaces plus, the 82 is geared more for straight math while the 85 has engineering and world uses more in mind. The 83 is an upgrade to the 82 with some better features and more capablites just as the 86 is an upgrade to the 85. The 83plus is a sup up version of the old 83 with newer technology.
This site is centered around the TI 83 since that's what we know best. If you own one the these others, you can still learn how to use it by looking at the 83. The interface and operating systems on all these are very close, though the 82 is much closer than the 85/86.
And then came the TI 89. The newest calculator from Texas Instruments, the 89 has the latest technology and a completely different operating system. Actually it has more than one version that can be downloaded (if you have a graphlink) so that even I don't really know how to use on very well. I consider the 89 on par with the 92 (the one that SAT banned) because it has just so many capablities: can work in symbolic as well as numberic, over a meg of memory, 3bit color instead of 2 with a higher resolution, heck the thing has an infinity key! As to date, the SAT board has yet to ban the 89, which suprises me since it is as powerful as the 92, but that may change.
well, that pretty much wraps it up for calculators in general.