I've just made a pull request for the internationalization part.
This adds a settings window where you can choose your language (based on the available translations files (.qm) in the "translations" folder).
So far there is only US English and German, where German has just 2 windows translated (for debugging). I expect a few changes for the UI until the first release, that's why I don't recommend starting translating yet.
A short how-to for translators and developers is in /documentation/translating.
I hope for later we can count on the OT/Bitcoin community to translate Moneychanger in many different languages

Any open points for internationalization expect the language I didn't think of?
I'll have a look at the HTTP-Interface now. I would inform you if I definitely start working on this.
Edit: I've also written a small Windows installer (very easy with InnoSetup), but I didn't have the time to test it and to build OT for Windows.