I've built a few simple desktop apps using Ruby, Tk, and Ocra.
There are plenty of possibilities, but I assume that you want to pick 
the best tools for the job by looking at your objectives. Without a bit 
of detail about the kind of application you want to build and its 
capabilities and portability, not to mention all the other priorities 
you might have (load speed, code-writing speed, memory size, API usage 
etc); it'll be difficult to know what the best approach is.

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