Hello *nixer,
Here are some things I do on my favorite browser Firefox/Icecat/Iceweasel/Nightly/etc..
(Note: with these settings FF might be more aggressive on CPU, it might even slow down the browsing)

**List**:
* Hide the menu.
* Remove the bookmark tool-bar and other things unwanted in the bar.
* Make the icons in the bar smaller, or remove it completely.
* Remove unwanted plug-ins and add-ons.
* Use external program to do things you can do outside the browser: aria2 as a download manager, adsuck as an adblocker,etc..
* get a nice personas, dark ones are great.
* always use the latest version of FF
* create a nice userChrome.css (this file may not necessarly exist and you might have to creat the dir chrome and the file in it).
* use userChrome to modify other websites (to your needs):
* Turn of anti-phising
* change some about:config (use these configurations at your own risks):

_NOTE_: after further research, I advise you to use configuration mania instead of most of the about:config changes.
**Configs**:

**Some nice add-ons** :
* configuration mania (to easily modify certain values)
* cookies manager +
* downloads in tab (to always put the download in a tab intead of a new window)
* firebug (the famouse one)
* fvd speed dial (a nice speed dial)
* https-everywhere (the boring one)
* live http headers (analyse http request)
* tamper data (another analyser)
* UAcontrol (change user-agent per site)
* vimperator (the famous one)
* Tab Mix Plus (helps you tweak your tabs)
* FEBE (a backup tool)
* FlashGot (To use an external download manager like axel, aria2, wget, and company)

**Related**:
[link to the browser screenshot thread](http://forums.unixhub.net/showthread.php?tid=449)
[link to the Arch wiki trips](https://wiki.archlinux.org/index.php/Fir...and_Tweaks)
[FF ramdisk](https://wiki.archlinux.org/index.php/Firefox_Ramdisk)