Use Custom New Tab to load any URL you want when a new tab is opened. This is the only add-on (to the author’s knowledge) that allows the user a preference to have the focus placed on a web page (like a search engine’s search box) or in the URL bar.
Want to have an easier time reading webpages? Try Blackout. This great extension for Firefox will dim the proverbial lights on Firefox to make reading webpages a lot easier. A white background with black text can be really hard on your eyes after a while. This add-on flips those colors for easier reading.
Reader is the ultimate reading tool for your Firefox that brings the Safari 5 Reader features to Firefox and provides you the best reading experience by transforming text on any website using fonts, colors, and layouts of your choosing in a clean and distraction free environment.
The add-on, Enhanced Middle Click, will display history menu, tab list menu or toggle various sidebars with middle mouse button. I often forget my mouse has a middle mouse button (I use the scroll wheel a lot though) however, this neat little add-on for Firefox has made me see things differently.
Image Search Options provides a set of highly customizable reverse image search context menu options. This Firefox Extension adds a set of customizable context menu options to the right click menu of images. These options allow for fast and efficient use of the IQDB, SauceNAO, TinEye, GazoPa, Ascii2D, Cydral, Yandex, Baidu, Google, (etc…) reverse image search engines.
HTTPS Finder automatically detects and enforces HTTPS connections when available. It also provides one-click creation and in-browser editing for HTTPS Everywhere rules.
This toolbar gives Google PageRank, Alexa, Compete and Quantcast Rank, pages indexed and backlinks in Google, Bing and Yahoo. Bookmark webpages at PickMeWeb.com or view similar websites at SimilarSites.com, Delicious, Digg and Tweet Count. It is a toolbar that brings a little ‘bit of everything to the table for a webmaster.
Need to add a ‘bit more to the vanilla Reddit experience? The Reddit Reveal add-on for Firefox will significantly reduce the need to click around to find out information about who has posted the Reddit posts you are looking at.
Reloaded Plus makes a lot of user-configurable changes to the behavior of the Firefox “Reload” button. If you like to make little tweaks to your browser to make your life easier, this add-on gives you that ability. The reload button is about to get a lot more functional.
While working, I usually keep Google Calendar open in at least one tab across my two screens. I like to keep it handy but I don’t know if I always need to keep it in front of my face. The add-on, Integrated Google Calendar, will make integrating Google Calendar with Firefox really simple.