Paint.Net is a nifty photo manipulation app and free as well.
And now to make it portable:
You will need http://legroom.net/modules.php?op=modload&name=Open_Source&file=index&page=software&app=uniextract
This will allow you to extract PaintDotNet.msi from the installer.
Extract this further using uniextract and you will have a folder PaintDotNet with the app in it.
Delete the copy of PaintDotNet.msi that is in this folder.
Now copy the complete folder to your pen drive and launch PaintDotNet.exe
If you use a portable app front end ie PStart then you can add the app to this and launch it from there.
It does require the PC you are running it on has the .NET Framework 2 installed (Which should be most up to date PC's) and it does add a registry entry when first run on a PC, so is not a true 100% portable app, but I still think it is better like this as it preserves the directory structure based on the machine it is run off (Basically it won't try opening a non existent drive),so if round a mates, you have got the app with you.
The registry information is screen position of window, last opened file, window size, which of 4 toolbars is open and not much else.
Installed size on disk 9.78 MB.
Never mind, just noticed Andrew does not accept .NET submissions.
Still dosen't stop the rest of us though!.
Sorry for wasting your time Andrew.