smali/baksmali is an assembler/disassembler for the dex format used by dalvik, Android‘s Java VM implementation. The syntax is loosely based on Jasmin’s/dedexer's syntax, and supports the full functionality of the dex format (annotations, debug info, line info, etc.)
Downloads are at https://bitbucket.org/JesusFreke/smali/downloads. If you are interested in submitting a patch, feel free to send me a pull request here.
See the wiki for more info/news/release notes/etc.