notes

useful pages for help:
http://developer.mozilla.org/en/docs/Building_an_Extension
http://kb.mozillazine.org/Setting_up_extension_development_environment
http://developer.mozilla.org/en/docs/Extensions

download xpidl: http://dietrich.ganx4.com/mozilla/gecko_sdk_osx.tar.gz
install prereqs (from http://developer.mozilla.org/en/docs/Mac_OS_X_Build_Prerequisites):
  $ sudo apt-get install orbit orbit-dev glib

unfortunately, you'll get errors from glib when building on an x86 mac complaining about the architecture.

compile idl file:
Makefile
GECKO_SDK   = /Users/eletuchy/gecko-sdk-mac-intel-1.8.1.3
MOZILLA_SRC = /Users/eletuchy/firefox-source/mozilla

all: xpt
xpt:
	${GECKO_SDK}/bin/xpidl -m typelib -w -v -I ${GECKO_SDK}/idl/ -I ${MOZILLA_SRC}/rdf/base/idl -I ${MOZILLA_SRC}/xpcom/ds/ facebook.idl


useful script to start FF using my dev profile alongside a normal copy of FF:
ari@Ari:platform/client/firefox$ cat `which FirefoxDev.sh`
    #!/bin/sh
    set MOZ_NO_REMOTE=1;
    rm "/Users/ari/Library/Application Support/Firefox/Profiles/949k0h9m.dev/compreg.dat" "/Users/ari/Library/Application Support/Firefox/Profiles/949k0h9m.dev/xpti.dat"
    /Applications/Firefox2.app/Contents/MacOS/firefox -P dev -console

to persist data across multiple windows, try http://www.xulplanet.com/references/xpcomref/comps/c_hashpropertybag1.html

to package:
. build.bat // works in bash ... zomg!