Firefox: If you install lots of add-ons, scrolling through them can be a bit of a pain, especially on a small screen. This little extension condenses Firefox's list of installed add-ons so you can see them all at a glance.
You may find it ironic that we have to install another add-on to make the add-on page take up less space, but it really does work well -- my add-on list takes up nearly half the space it used to, making all of my add-ons viewable without scrolling. It still lists all the same options, buttions, and info as it did before, just more condensed -- and you can expand it if you want to see more. Simple and effective. Hit the link to try it out.
Cleanest Addon Manager is a free download, works wherever Firefox does -- without even having to restart the browser.
Cleanest Addon Manager [Mozilla Add-Ons]