This tool extracts an 'R.txt'-style resource list from a compiled Android application. The input must be Java bytecode (use dex2jar if necessary). The output is compatible with the 'R.txt' format used in Android archive (.aar) files.
Usage: extractar <classpath-directory-or-jar> <fully-qualified-name-of-R-class>
WARNING: This tool loads and initializes the target 'R' class (which means that it executes untrusted code) without sandboxing it. A rogue class can attack you. Decompile and analyze the class or drop privileges before invoking this tool.
Visit the XDA thread for details: http://forum.xda-developers.com/showthread.php?t=3060854
ExtractAR is free software (GPLv3+)