There have been several highlighter extensions I have seen over the years for Firefox, however this one might be my favorite.  The ultra light-weight Highlights add-on for Firefox simply highlights selected text on web pages with a right-click of the mouse.

To highlight text on a web page, select the text, right-click (‘Ctrl+Click’, on Mac OS X) and select ‘Highlight’ menu from the popup.  The default yellow highlight color can easily be changed, by clicking the “Highlights” icon on the [...]

The idea of having a Firefox extension that gives you content related to what you are looking at is nothing new really, however I have found a Firefox add-on that will help you get it done in a new and exciting way. 
Headup underlines words on pages when you browser.  When you hover over those words, you get relevant content from popular web services. 

Technically speaking, they  “presents you with textual and rich media content related to the [...]

Want to be able to comment on any web site out there on the Web, without the permission of the web site in question?  Reframe It opens up a new portal of communication, by allowing you to communicate through specific comments next to the web site you are referencing. 
Why just send a simple text-based note, when you can send that and the web site you are talking about all in one swift, easy to access movement?  Here is the [...]

What is WebMynd?  It is all about personalizing your search – with colors.  Ok, now before you think this is some new age hippy thing, hear me out.  This add-on for Firefox will help find and keep track of information from a number of different sources.
What sources does it support?  We have:  YouTube, Wikipedia, Flickr, Twitter, Amazon, Economist, CNN, LinkedIn, TechCrunch, Hacker News, Digg, Reddit, Google Books, Fluther, Delicious, Yahoo! Shopping, Scribd, Backtype, and Youlicit.
The easiest way to explain [...]

It seems like I am always doing research on one thing or another, for a future article or a future project of mine.  There are not that many tools out there to help you collect your information and save it for later.  The ScrapBook extension for Firefox is one of the few.  It is simple and also allows to save web pages and organize them as you see fit.
Here are some of the features ScrapBook provides…

Save Web page
Save snippet [...]

Joe Wilcox over at eWeek has put together a pretty interesting graph charting the adoption rate for the web browsers out there in 2007.  The graph and story along with it are both pulling information from the recent Forrester Research report, “Enterprise Desktop and Web 2.0/SAAS Platform Trends, 2007.”

As you can see Internet Explorer is still pulling head as you would assume it would do, but Firefox still is holding a healthy share of the market.  Internet Explorer 7 [...]

What in the heck is Zotero? It sounds like a snack food brand!
Zotero [zoh-TAIR-oh] is a free, easy-to-use Firefox extension to help you collect, manage, and cite your research sources.
Alright, that is good to know. For many of us, doing research can be a pain in the rear so i am all for any tool that promises to make the experience easier.
+ Download and Install the Zotero Extension for Firefox!