Put this in your ~/.emacs file:
(fset 'scroll-up-lines
"\C-u2\C-[xscroll-up\C-m")
(fset 'scroll-down-lines
"\C-u2\C-[xscroll-down\C-m")
(global-set-key [mouse-5] 'scroll-up-lines)
(global-set-key [mouse-4] 'scroll-down-lines)
Bad. Ass.
I tried getting it to focus the buffer it was over instead of having to click once (when you have a window split) but couldn't quite figure it out. I'll keep working on it in my