What is the best open source, desktop application software?

[jskitz]

For a project I'm working on, I'd like to build a desktop application that can run on Mac, Linux and Windows without too many modifications. I would like the application to be built with open source software. The application I want to build is a simple uploader, with thumbnails representing the files in the list. What would you consider the best desktop application software for a project such as this? I'm currently leaning towards WxPython. Any thoughts?

[greenlblue]

Why not build a web app? It will run practically on any platform that has a browser which is basically everywhere. That's basically what I do lately. Anytime I think of neat idea I first prototype it in firefox with the help of firebug and more often than not it turns out to be good enough.

[jskitz → greenlblue]

I've definitely considered that as a possibility, however part of the application is to discover (search for) files on your system, and then upload specific files based on requests from other people. I was thinking that this would be slightly prohibitive in the web browser, at least from what I know from building Java applets and Flash based uploaders. If I were to do this in the browser, I would want to use purely JavaScript, but I'm unsure if this would be powerful enough for what I want to do.

[braindead_in]

XULRunner with a custom XPCOM component is another option. However for a simple applications WxWidgets is the way to go. Mono is another option.