Chrome/Firefox: Ever been reading a site and wish not to go back to the last page you visited, but the last page in that web site's hierarchy? These two extensions add a button to the address bar to do just that.
One of people's favourite features in the Google Toolbar for other browsers (yes, a lot of people actually liked it) was the ability to jump up one level in a site's hierarchy. So, if your friends send you an image URL, you can quickly hit the up button to go back to the actual site that hosts it. Or, if you're browsing a forum like Reddit, you can go back to page 1 of a thread, or go back to the main site entirely — even if you didn't navigate there first. It was always one of the best features in Windows Explorer, and now you can get it in your browser too.
For Chrome: Up
Chrome users just need to download Up, which is a simple button that lives in your extension bar (or, if you prefer, your Omnibar) and you can hit it to navigate back in a site's hierarchy. It's simple, but a nice time saver if you find yourself doing it often.
For Firefox: Uppity
We've actually featured Uppity before, but it's worth another mention as we re-cover this ground. Uppity adds a button to your toolbar that, when pressed, takes you directly up one level. You can also hit the arrow icon next to its button to view the site's hierarchy from where you are, so you know where each level will take you (and you can jump up more than one). Note that after you install it, Uppity won't automatically show up on your toolbar — you have to go to View > Toolbars > Customize and drag it there yourself.
Both extensions are free downloads for their respective browsers.