This is probably old news to most, but I was happy to discover that the program iScroll2 allows older portables to use the two-finger scrolling and two-finger right click features. It seems to work well on my 1.33Ghz 12" PowerBook. The only difference that I can see between the functionality it provides and that included with the newer portables is that the two-finger right click feature requires you to use the physical trackpad button. Apple's implementation of this only uses the trackpad button if you don't have trackpad clicking enabled. If you do, you have to tap the trackpad with two fingers to activate a right click. I personally prefer using the trackpad button even though I have trackpad clicking enabled.
http://www-users.kawo2.rwth-aachen.d...fazz/iscroll2/
This and
enabling safe sleep have given some new life to my older PowerBook. (I love finally being able to change batteries without shutting down or being connected to AC power.)