The stuff you need to install programs on your calc.
TI-84 Plus or newer
You need a Mini-USB cable like this one from Amazon.
It's exactly the same as the charger included in the box.
Any calculator with a headphone jack lookin' port.
You need to buy a TI Graph Link cable that looks like this:
They are hard to find at major retailers. Ebay is your best friend here.
This page on ticalc.org is really helpful: ticalc.org/hardware/cables/
There are four different softwares to let you install things on your calc.
All of them are open source except for TI-Connect
ticalc.link is a website that lets you send files to your calc over WebUSB.
It works on all platforms (as long as you're using chrome), which is a huge plus for Chromebook users.
This is the most convienent way to send files to your calc but it is still experimental, but if it works reliably with your calc it is awesome.
The current list of supported calculators is available at the bottom of ticalc.link.
prgmTRANSFER is a program that lets you transfer files over MTP.
This lets your calc show up in your computer as a normal flash drive! You need to install the program on your calculator first via one of the other methods before you can use it.
The current list of supported calculators is available at the prgmTRANSFER website.
It is not nearly as convienient either ticalc.link or prgmTRANSFER though, and doesn't work on school chromebooks. Although, it does work on non-school chromebooks albeit not well and only for TI-Connect CE version.
TI-Connect supports all calculators up to the TI-84 Plus while the newer TI-Connect CE supports the TI-84 Plus or newer.
TiLP is the original alternative linking program for TI calcs.
Unlike TI-Connect its main feature is that it works on Linux but does not have Chrombook support of any kind.
You can find the list of supported calculators at the Features page on TiLP's website.