Portable App Development

Newbie here,
I'm finalizing my U3 version, and figured I'd do PortableApps too. I'm not yet writing my script, but wanted to build the hooks into the main app first. With U3, I'm able to use Environment Strings to find path info, such as:
IShouldStoreMyDataHere := GetEnvironmentVariable('U3_APP_DATA_PATH');

Can I do this with NSIS? Or do I need it in conjunction with something else? Let me know if there is a sample app that does this. I looked through several, but maybe I didn't know what to look for.

I have written something for my company to help them secure documents on a USB stick. I'm getting on in years now, and never really progressed from the days of DOS batch scripts, so this is what I end up using, its not elegant, not clever, but it just about does what they want.

Today I found Portable Apps, and wondered if its something that I could use because its so much better than anything I'm likely to be able to create.

Does anyone have any suggestions or sites that I could use to learn NSIS?
Thanks
Ben

Is it possible to make parts of the registry portable? The most evil part of windows is the registry!!

Sorry that I'm always the guy posting about Apps leaving files...
But
The Backuptool is leaving a folder called
nsr37.tmp (or something like that)
and a
registry.dll
inside.
So its the NSIS registry plugin.

Why does my Portable NSIS always makes an error with John's
"RequestExecutionLevel user" ?
Do I have an old version of NSIS?

Is it possible to make a shareware product a "Portable App"? What are the steps?
Thanks for any reply.

Lifehacker has a post for a (portable) program that makes your screen look like you placed a drop cloth over it. All the screen is blanked out (transparency and color can be set) and only the task bar and your active app are "normal"...

http://lifehacker.com/software/distraction/lifehacker-code-dropcloth-win...

If you are interested...

Rich

I just discovered Steves Libertà page at PortableApps.com (For the curious, it's here)
So my question is: Is there any list of all the project pages here or are they like eastereggs on DVDs, only revealed by people who found them by accident and reveal their existence to the public like me

I have a few apps which are basically portable (they run from a single directory, without saving anything to the registry or local disk). For example, ToME (roguelike game), 4NT (command processor, commercial, "inikey" version"), TCI (tabbed console interface, commercial, "inikey" version). They certainly don't make enough of a mess for me to be bothered working out how to write a full-scale "Portable" version.