Looking to make Firefox a little darker, and perhaps even more mysterious?  Look no further than the BlackFox theme for Firefox.

This is one of the few dark Firefox themes I could see myself using on a regular basis.

Very clean and easy on the eyes, two things you can say about the ArzoFox theme for Firefox.  I like themes that can make the browser experience better just by touching up a few things.  The gradient background, mixed with the colorful icons is a great combination that is really hard to beat.
  
Like what you see?  You can pick up the ArzoFox theme on the Firefox Add-ons web site.

If your looking for a mostly 2D, grayscale and compact theme for your Firefox browsing ways – look no further than the Two Dimensions theme.  As you can see with the screenshot I included, it is a very slick skin for your Firefox browsing ways that will not disappoint those of you who like to keep things simple. 
It would fit nicely, I think, in my list of lightest popular themes for Firefox.  Who knows, it might earn its spot [...]

I can’t get it out of my head that this modern and compact theme sounds like a great magician.  I want to call it the Amazing Stratini!  What is its first trick?  To turn your Firefox installation into a better looking browser.  Actually, there are now two different flavors of the Stratini theme, one is the original (which is more compact) and the other is more padded and spaced out.
Here is a little more about the themes in question from [...]

Wanting to save some space in Gmail, or perhaps you’re just tired of the text-based main links to browse around your e-mail account?
The GMail Compactor user script will help you reclaim that space with style.

As you can see, from the picture above, after you install this Greasemonkey user script, everything from your Compose Mail link down to your Contacts link are now minimized into very pretty icons.  As an extra benefit, you also still get the count of how many [...]

One add-on I keep adding on is Tiny Menu, due to the fact that I like to have a minimalist browsing experience.  However, I have found one extension that does an even better job than Tiny Menu at compacting the standard menu bar down to one small popup menu, Compact Menu 2.
The major benefits Compact Menu 2 has over Tiny Menu are:

An even smaller footprint (one small blue globe to access your regular menu bar items)
You can move it [...]

Based around the hmmXP visual style for Windows, the hmmXP theme for Firefox gives you something familiar (that sort of Windows 9x look) with just a touch of visual appeal.  The theme is compact, but doesn’t feel as if everything is squeezed in just for the sake of squeezing it in. 

As said by the author of this awesome theme, a lot of love has been put into it, so that it looks great in any windows theme.  If [...]

Bigger is not always better.
Sometimes keeping things a little more compact means that you have more room for the more important things.
That is where the Classic Compact Firefox theme is so valuable. It gives you that classic look of the Firefox theme but in miniature form.
A very compact version of Firefox’s default theme, which minimizes vertical space consumed by menu, tool, tab, find and status bars as much as possible without hurting overall appearance.
+ Download [...]