Related link: http://weblogs.oreilly.com/
For users of Mozilla, there’s a huge realm of additional plugins and techniques you can use to enhance your browser’s power. First off, appearance wise, I like subdued minimalism. I use the “Cold Mettle” skin for Trillian (when I’m stuck using Win32, that is), and I use the Pinball scheme for Mozilla - subdued and minimal.
As a web designer, you should attempt validity in your markup at all time. Checky is invaluable in this regard, giving instant access to dozens of validators, ranging from CSS, HTML, XHTML, accessibility, and RDF. Configure the services you want, jump to a page, and hit F12. I prefer tab loading, so up’ll pop four new tabs with my validation results waiting. Very time saving.
As a web programmer or server administrator, it’s often helpful to see the actual HTTP headers that are being passed from your server to the browser. livehttpheaders is your answer, offering a new tab under “View Page Info”, as well as a live viewer in a separate window. If you’re using Mozilla in the first place, this can save you time from jumping into a shell to issue a HEAD.
For those with many bookmarks (myself, I’m rounding 1600, all anally categorized), check out bookie, a server based data store of your favorites. It’s a little bit more than a plugin - you’ll have to run a Java application on a central server, but it can prove handy if you’re jumping from machine to machine (and don’t want to fiddle with email attachments - my current lowtech solution). You can dump more power into your Bookmarks with Bookmark Keywords (and here and here). Alternatively, you could make your own custom toolbar to further distinguish your collection.
Did I miss any? What has increased your browsing power?