Chrome: If you often have to go back into your browser's history to find "that one page you were looking at", you know how annoying it can be. History Calendar makes it easier by letting you sort your history by date.
If I foresee needing a webpage later on, I'll usually bookmark it or create a shortcut on my desktop, but sometimes I forget—or sometimes you just need to revisit a page unexpectedly. When that time comes, it can be a huge hassle to sift through pages and pages of your Chrome history to find that site—especially when searching doesn't help.
History Calendar adds a small calendar to the upper right-hand corner of Chrome's History page, so you can filter your history by date—if you know you visited that site last Saturday, for example, you can view just the sites you visited last Saturday, really helping to narrow down your search. If you're a big history user, it's a good extension to have installed (and maybe disabled, so you can call on it only when you need it).
History Calendar is a free download, works wherever Google Chrome does.