I just recently got my N800 and I am very impressed with the device. I have also been lurking here trying to soak up as much as possible so as not to ask dumb questions.

What I am most interested in is learning how to port applications, I have no programing skills to speak of yet, but I was hoping that this device would be a good way to learn. I am very patient and not afraid to read (I am a librarian) so I would like some pointers to get me started in the right direction.

My first question is whether there is a developing environment that will run on an older G4 mac? Preferably something free.

Second would it be beneficial to compile something that has already been done to help myself understand the process? If so, what would be a good candidate for this.

Finally is there any way that non coder (right now) can help out, this is great device and it appears to have an active community that I would like to be a part of

Check out Python and C++, majority of the programs are written in C, however, you can learn Flash and skip those two... what type of apps are you inclined in creating?

ruby or python, both ported to N800 are a good way to start. Also they're available in OS X
They're both good, simple and easy but this doesn't mean that don't require hard work to learn.
It's important to have clear ideas about development stuff like objects, functions, variables, logic, flow control, classes...
Tere's a project good for this called Alice:
http://www.alice.org/
Chris Pine's "Learning to program" helped me also.
http://pine.fm/LearnToProgram/
with this you have enough for a couple of weeks

Right now I am mainly interested in learning what is possible, I started my undergrad as computer science major but switched to psychology due to lack of girls before I switched I was working with turbo pascal, I would like to give it another crack and this gave me an excuse to justify the purchase of a gadget.

Not knowing anything about the dificulty of programing, I would like to bring this game http://ostermiller.org/ladder/ to the N800

I myself am learning how to code C and C++ on my N800 - using PyGTKEditor to create source code, GCC to compile\link, and Evince to read eBooks on C/C++). I hope to eventually learn how to use the GTK+ API to create GUI applications for Maemo and any other operating system.

But other more modern languages mentioned by others might be better.

I wanted to mention that you could download the (now free) Turbo Pascal v5.5 from Borland and use the DOSBox emulator to run it on your N800. Though Pascal is mainly a learning language and I am uncertain how close it's syntax is to Borland's Delphi's language.

Sounds like this uses java, which is not that well supported on the NITs yet. I haven't tried to fiddle with it myself yet, but see here:
http://maemo.org/community/wiki/javalanguage/

That game seems simple enough that I would think if you can get any java solution at all running on your NIT that it should "just work".

Check out Jalimo

I haven't done anything with it except write/run "Hello World" but it worked beautifully for that. I haven't looked at the ladder game but if the interface is purely console/text based, then it should compile and run with few to no problems

My suggestion and intended development path is to learn Python and use the Eclipse plugin from http://pluthon.garage.maemo.org/

This looks like the simplest way to get up and running if you're running OSX. Mind you, I haven't tried it, but it looks to be simple and platform-independent.

Currently when I want to kill time writing java, I use PyGTKEditor to write the source code, and then compile the code using the JXXX Compiler Service and then run it using Jalimo, all from the device

Alternatively, you could set up Scratchbox (the provided maemo SDK) in a virtual linux machine utilizing some program such as Virtual Box

Hope some of this helps! Happy coding!

UPDATE: I just tried running the ladder.jar file and it actually looks promising. It didn't run, but the only thing it complained about was the lack of the AWT library in the Jalimo runtime. This is a known incompatibility, (Jalimo requires that you use the SWT libraries instead) but should be easy to port the code over, provided the developer utilized good modular programming when he created the game. I'm actually quite tempted to download the source and try it... I would for sure if I didn't have finals coming up