these are some links worth sharing:

list of dalvik opcodes:

smali / baksmali project page. great tool for disassembly:

apktool project page. uses baksmali / smali but also can decode resources:

good community for mobile apps:

dex2jar for converting dalvik code into java code, sort of:

excellent place for reversing forums, blogs, tutorials:

detail-rich reversing blog with lots of android content and general reversing:

a good start for looking at native assembly: