On my MacBook I have a Bluetooth mouse that I use when I'm at my desk. Otherwise, I use the trackpad. In Firefox, by default when I scroll using the mouse, it only scrolls one line at a time. My mouse doesn't have any software drivers that can make it scroll one screen at a time and OS X doesn't let me change this either.
In Firefox, I can set mousewheel.withnokey.action to 1 (default is 0) to scroll one screen at a time with the mousewheel. This works well when I'm using the mouse, but when I use the trackpad it is too much and I want to go back to the default behavior. I could use about:config and change this pref each time but that is pretty tedious.
Switch ScrollWheel Behavior plugin. Yes, the name is lame and so is the icon (you'll have to install to see it since I'm too lazy to put it here. This extension adds a right-click menu item and a Tools menu item that will toggle the value of mousewheel.withnokey.action between zero and one (yes, there are other values but I don't care).
Hopefully someone else finds this useful. If so, leave a comment and I'll probably be motivated to add a toolbar icon that can be used as well as creating preferences for it so you can also manage overriding the system default for the number of lines to scroll.