Cross Platform App with Localization
Tcl/tk has excellent unicode support, and a very workable message catalog library. It's also highly portable to all major platforms (and several not-so-major platforms). In addition, you have the option of packaging your whole app up as a platform-dependent runtime (tclkit) and platform-independent application file (starkit), or combine the two into platform-specific single-file executables (starpack). In your case I'm guessing you might want a third file that is the audio for a specific language. So, you could have the main application and "language packages" that contain the message catalogs and .mp3 files for each language.
Since you mention Python as a tag, another choice would be Python with Tkinter, wxPython or pyGTK. Python's unicode support isn't as clean as Tcl's, though, and requires a little more work to support.
I am interested in developing a simple language learning (French, German, etc) desktop application to assist users in learning vocabulary by seeing and listening (via MP3 files) to words simultaneously.
I done some programming when I was younger and see this as a long term project to get back into programming by developing an application to help me with language learning that I can share with others.
In addition to helping English speakers learn other languages I would like the application to be localized so that the interface (and audio files) could be switched to assist others in learning English.
I am very open minded and have read about Eclipse, MonoDevelop & NetBeans to develop a cross platform GUI. I have also read a lot of good things about Ruby and Python so would be interested on any advice/recommendation on which combination of language and tools I should use.