Compile this script in Applescript Editor and run it. It will let you enable or disable rubber band scrolling.
display dialog "Disable or enable rubber banding?" buttons {"Enable", "Disable", "Cancel"} default button "Cancel" with title "Rubber Band Control" giving up after 15
if button returned of the result is "Disable" then
do shell script "defaults write -g NSScrollViewRubberbanding -int 0"
else if button returned of the result is "Enable" then
do shell script "defaults delete -g NSScrollViewRubberbanding"
end if
[kirkmc adds: Well, it seems that disabling rubber band scrolling is quite popular! After a first hint, then yesterday's hint about disabling rubber band scrolling in iTunes, here's another, perhaps easier way, using AppleScript.]

