UPDATE: As I promised yesterday, I added some more links to the list.
Ufff. Not much documentation around! Best advice? Decompile, and read, and tweak, and see how it did, and start the cycle again and again. But you did not ask for that advice, right? 😉
Now, there are a few places out there that wil lhelp a little bit:
http://androidcracking.blogspot.com/search/label/smali
This is the best one. I even asked the guy a question and he answered very quickly, so go and take a look.
http://pallergabor.uw.hu/androidblog/dalvik_opcodes.html
Very comprehensive table – good reference!
http://webchat.freenode.net/?channels=smali
I never tried it, but it’s on the google code page of the baksmali author ( http://code.google.com/p/smali/ )
http://forum.xda-developers.com/showthread.php?t=777707
Lastly, this is a post I made some time ago describing some hacks to the Captivate camera.
You can follow the diffs in there as I comment a little bit on what each .diff file is doing. The good stuff starts at the post #20.
http://www.slideshare.net/paller/understanding-the-dalvik-bytecode-with-the-dedexer-tool
Interesting slide show with some basic concepts. Good way to start.
http://sites.google.com/site/haynesmathew/home/projects/dalvik-notes
Even more low level than the typical .smali. A reference for later, but a good read.
http://jasmin.sourceforge.net/guide.html
Smali syntax is based on Jasmin, so this gives good concepts.
http://groups.google.com/group/apktool?pli=1
Some discussions there are worth reading through. Also a good place to search for when you’re stuck in something.
And last, but not least, the most helpful trick I used: start coding very basic classes and methods in java, compile them and then baksmali your own code. You know exactly what it does, so it will be a lot easier to follow.