For those who want a jumpstart on how to use FreeBASIC:
http://www.freebasic.net/wiki/wikka.php?wakka=TutGettingStartedQB
http://www.freebasic.net/wiki/wikka.php?wakka=TutHowToProgGame1

I only read those two to make my port from TI-Basic to Freebasic.
The first link shows how to output text, draw lines,draw circles, rectangles.
The second one is more interesting. It shows you how to create a game loop by moving a circle.
It'll introduce you to FB's "GetKey", "ClrHome", loops and the declaration of variables.
They don't take long to read either, it's great!

Look at this page to get a quick peek at all the commands:
http://www.freebasic.net/wiki/wikka.php?wakka=CatPgFullIndex

Hmm, some of it reminds me Casio calculators...

If it's similar to TI-BASIC and Casio BASIC, maybe I could learn it easily

Well that's the beauty of it. It may not have the exactly same syntax but It certainly does "feel" like TI-Basic.
I'm really developing to become a FreeBASIC fanboy now.  
You could also "setup" FreeBASIC to behave alot more like TI-Basic on the calculator.
Here's a quick tutorial:
NOTE: You can get alot of this out of the previously mentioned tutorials too.

If you add the following line to the top of your FreeBASIC source, you get a 16x8 character screen like the one on your calc.
screenres 136,72
If you add these lines to the top you can use the very responsive GetKey from FB(there's also a slower one):
   #include "fbgfx.bi"
    Using FB
The very responsive GetKey works just like in Axe
MultiKey(SC_KEY)
If you want to use certain variables you have to declare them.
You're probably not used to this in TI-Basic but it's standard fare in computer languages.
DIM as integer A,B,C
DIM as string Str1,Str2It's pretty straightforward. Here's a link to the datatypes.
http://www.freebasic.net/wiki/wikka.php?wakka=CatPgStdDataTypes

If you want to store variables:
A=10
str1="abc"

The pause command in TI-Basic becomes
Sleep
If you want to pause for 100 milliseconds
Sleep 100,1If you don't add the ",1" it'll wait for 100 milliseconds OR until a key is pressed. the ",1" disables the latter.

ClrHome becomes
Cls
If your hesistant about using FB's syntax and rather want to use TI-Basic's syntax, you can just add a subroutine to the beginning of your code.
e.g for ClrHome

Sub ClrHome
cls
End sub
And now you can use ClrHome in the same way you use it as in TI-Basic!
i'm going to go out on a limb here and say that you can do this for about every TI-Basic command except:
-the (unconventional) storage of variables e.g 10-> B
-Conditionals
-Loops

Here's a subroutine to use the Output command.
Note that I use output1(Y,X,"text") instead of output(Y,X,"text") because there already is a (different) function called output in FB, so I can't just replace it with mine.
sub output1(Y as integer,X as integer,text as string)
locate Y,X
print text
end sub
Also be aware that FB is certainly not limited to the stuff I'm showing you.
Check FB's projects page to see what FB is capable of.
http://www.freebasic.net/forum/viewforum.php?f=8
I kinda smirked at the gameboy emulator thing.
*imagines writing a gameboy emulator in TI-Basic *

Very cool. I'll add that to my Tutorials page.

Ok so if we call a command that is not the name of any FreeBASIC command or name used, it will interpret it as an actual sub-routine? Seems kinda nice. Someone could easily write a set of sub-routines that lets someone use pretty much all game programming TI-BASIC commands.

That would be hella awesome Or maybe a crossover language for people who know calc programing but want to move onto computer programing

And I think there was a topic somewhere around here about making an online calc simulator ... what about just a simple TI-BASIC emulator? It would be really helpful to people without an emu on their computer.

One other question about FreeBASIC: if you want people to be able to play your game, do they absolutely need to install FreeBASIC or can you make them standalone executables like Visual Basic and RPG Maker (in the latter, you needed to use an undocumented trick to remove dependencies, though)?

Ok good. With one of my old VB games, I discovered it requires me to download some OCX files to play them and it won't tell me where to put them (in the system folders it doesn't work in Windows 7 64 bit)

Sadly, no. It's a computer program (definitely Windows, Idk about Linux or Mac OS)