I'd like to translate my GUI into other languages. Unfortunately I don't speak Mandarin, Spanish, Arabic, or any common language other than English.
The technical hurdles are no problem... what I'm wondering is: How do you get the actual translations?
Amazon's Mechanical Turk? Google Translate? Pay an actual translation company?
What you're looking for is called "Localization". Generally, you have to do the actual translating part on your own, or find people to do it for you. Translating text is just too ambiguous for most software to do it reliably.
You can try RentACoder.com as well. There's quite a bit of translation work going on there really cheap.
Or you can just blog about it, or depending on your application's availability give the users the possibility to contribute voluntarily.
Your going to have to hire a native speaker who speaks your native language as well.
Another thing to consider is that your layout will likely have to change. Buttons that used to be big enough may be too narrow. Users may expect to see things in a right to left fashion and so on. There's a lot involved to do a proper localization.
There are companies that specialize in this kind of thing. Maybe one of them would be the way to go.
If you can afford it you can hire people who specifically translate software. Search for "software localization" and look at professional localization services companies (I found few on first page in google). They normally have bunch of translators for dozens of languages on payroll.
This will cost you though.