George, I noticed nobody answered your question, so I thought I would chime in.

Your TI-84 is designed to have a user go into a particular mode (programming mode) and enter keystrokes that are "stored" for later re-use.  In the lingo of programming, this is called a "macro".  It is a way to play back a sequence of keystrokes in the same way each time.  Some such macro programming environments also allow the user to choose a different set of keystrokes based on an interim result.  Actual programming is vaguely similar to macro building, but instead of keystrokes, you are putting together statements in a programming language.  Various statements accomplish specific things, just as the keys on a calculator provide a (very limited) set of things that the calculator can do.

Programming (as opposed to building a macro) involves learning a programming language.  In many cases (chumby included), this programming language is specific to the environment in which your program will run.  In the case of chumby, the environment in which the program runs is called "Flash".  Flash is an environment invented by the company Adobe (the Photoshop people) that was originally intended just for making swanky web sites. 

In a more mainstream use of Flash, a user is on a desktop computer using a standard web browser.  They navigate to a page that includes a Flash program.  The browser recognizes the part of the page that is a Flash program and downloads it. It sends that program to a program on the desktop computer called a "Flash Player".  The Flash Player runs the Flash program, and the visual results of the Flash program show up in the browser window.

With Chumby, there is no web browser, but there is a Flash player.  A means is provided (via the Chumby website) to tell your specific chumby to download a specific Flash program and send it to the Flash Player on your chumby.  The Flash program that gets downloaded has access to information on the internet and it can determine which types of information it will download and how it will display it on the chumby.

In order to learn how to program a Chumby (in the standard/supported way), you would need to become familiar with Flash programming, which you can do by going to Adobe.com and learning about Flash development.  There are also bookshelves groaning from the weight of Flash books in any library or bookstore.

I would suggest picking up such a book and learning to make a flash webpage as the most straight forward way to learn chumby programming from scratch.  Since you can't buy a chumby yet, this would be a way for you to get started "early".

cheers,
jp