History Tree is a (Windows only) Firefox add-on that makes your browser history easier to navigate by displaying it as a tree diagram. It gives you a quick visual layout of the tabs and windows you've opened, and lets you find the page you're looking for even when the browser's back button won't reach that far. You can also switch to a page thumbnail view that makes it easier to find the page you need at a glance.

Like any good history browser, History Tree has a search function, but you might not need to use it. Its information is color-coded according to whether each page is currently open and whether it's accessible via your back button. Each page in the tree is also timestamped, so you can look for pages according to when you last saw them. If there's a page you don't recognize, you can click on the ? button or a thumbnail. If the tree's too cluttered, you can collapse part of it, display just one tab at a time, or set a filter to show only part of your history (only your current open tabs, for example).

[via Ghacks]