Kivlad is a decompiler for Android's Dalvik binaries, with a highly customizable web-based navigation interface. Unlike existing decompilers for Dalvik, it works natively on Dalvik bytecode rather than converting back to Java bytecode; this means much higher quality results. Also unlike other tools having a static GUI, it takes in Dalvik binaries and gives you HTML that can be themed and extended as you desire.
This is very much an alpha release and while it will be production-quality in the near future, we wanted to give the community a taste of what's to come.
Kivlad works with Ruby 1.9 on Windows, Linux, and OS X. You can download it here and follow the readme to get started.