Any collaborative tool/website to localize an Android app?

I've written a tool to convert between Android XML resources and .po files:

http://blog.elsdoerfer.name/2010/04/08/android2po-managing-android-translations/ http://github.com/miracle2k/android2po

I'm using this myself with Pootle, and it works well enough, though I'm not really all that happy with the Pootle UI. Crowdin is in fact much better in that regard.

I opted for Crowdin. It allows the admin to upload the XML files, and then anyone can translate to any language.

Translated files can be downloaded in a ZIP archive.

It is free for Open Source projects.

The UI used to be really slow, but it has got better recently.

One tool was not yet listed so far - Weblate. It has native support for Android string resources and is already used for several apps (for example OsmAnd). Though it requires you to use distributed version control system (preferably Git).