Firefox only (Windows/Mac/Linux): If you like the concept of bookmark tags introduced in Firefox 3 but just can't seem to get into the habit of using them, Firefox extension Tagmarks adds tag images to your awesome bar for quick and easy bookmarking and tagging. Once installed, you'll see several new images next to the default star when you hover your mouse over the star. Click one to both tag and bookmark that page in one fell swoop. You can click on as many of these tags as you want, and when you view your bookmarks, you'll notice text tags have been automatically assigned. Tagmarks is free, works wherever Firefox does. Hopefully we'll see a more customizable version of Tagmarks in the future.Featured Firefox Extension: AutoPager Automatically Loads the Next Web Page Inline
Firefox only (Windows/Mac/Linux): The AutoPager Firefox extension automatically loads the next page of a site inline when you reach the end of the current page for infinite scrolling of content. By default AutoPager works with a ton of sites, including Lifehacker, the New York Times, Digg, and, of course, Google. At first blush AutoPager is a little difficult to understand, but just set it as Always Enabled by clicking the AE link on supported sites and it'll take care of the rest. If you want to add your own custom autopaging to unsupported sites, the site wizard feature makes it easy (first pick the Next link, then pick only the content you want loaded (in Lifehacker, for example, the posts). AutoPager is free, works wherever Firefox does. For similar functionality, check out previously mentioned Repagination.Featured Firefox Extension: RIP Permanently Removes Elements from a Web Site
Firefox only (Windows/Mac/Linux): Firefox extension Remove It Permanently (RIP) selectively removes any element from a web site. If you've ever looked at a site and wished you could get rid of some unsightly image or an element that throws off the flow of a site, just right-click it with RIP and remove it permanently. You can select to remove it from that page only, all similar pages, from the web site, or from the entire domain--in addition to a few other options. Don't think of it as an ad-blocker--you should just install an extension like AdBlock Plus if that's what you're looking to do; think of it more as an all-purpose annoyance remover. Unfortunately RIP hasn't been updated for Firefox 3.0.1, but this tweak will do the trick until it has. RIP is free, works wherever Firefox does.Featured Firefox Extension: Drag & Drop.io Makes Sharing Files Dead Simple
Firefox only (Windows/Mac/Linux): The Drag & Drop.io Firefox extension makes it easy to quickly share a file in Firefox 3 with previously mentioned file sharing site Drop.io by simple dragging and dropping the file in your browser. The best part of the extension is that you don't need to go through any tedious Browse for file dialogs to upload files you're probably already staring at anyway. The extension has a few subtle differences in how you can use it to upload and share files, so check the demo video for a full overview. If you want to be able to drag and drop files into any upload box at any site, check out previously mentioned dragdropupload.Featured Firefox Extension: Google Redesigned Facelifts Gmail and GCal
All platforms with Firefox: Globex Designs, makers of the popular Gmail Redesigned skin, have released a standalone Firefox extension which applies the style without Stylish (or Better Gmail and/or Better GCal). Download the extension to completely redesign your Gmail and Google Calendar with the latest and greatest style from Globex.Featured Firefox Extension: Evernote Web Clipper Adds Content from Any Web Page
Firefox only (Windows/Mac/Linux): Free, cross-platform note-taking application Evernote offers a handful of tools for clipping content into your Evernote account, including the newly released Web Clipper Firefox extension. Aside from a Clip to Evernote entry in the right-click menu and a new toolbar button, the extension works just like the Clip to Evernote bookmarklet (perfect in its own right if you don't want to install another extension). The inline dialog autocompletes tags and adds the item to your Evernote account without interrupting anything you're doing. A Web Clipper keyboard shortcut would be nice, too, but the extension or bookmarklet are a must-have for anyone getting started with one of the best note-taking tools available.