I have been studying this:
http://www.davespace.co.uk/arm/effic...arm/index.html
VERY enlightening. Some things coded in C can be horribly inefficient compiled with arm GCC, unless you do some interesting adjustments to the C code. Also check out the ARM assembler tutorial there.
No new code yet, but I plan to do a fancy audio/video player with touchscreen (and keyboard) GUI one of these days Real Soon Now.