Chrome/Firefox: Dropbox is a crowd favourite in the file-syncing tool category thanks to no shortage of uses. The site kind of sucks to navigate though. Fortunately, you can make it a little less terrible with Dropbox Plus.
This userscript adds a file structure menu to the left-hand side of the Dropbox website. While most of us may not use the site that often, the limited file-navigation features can be extremely jarring on those rare occasions you do need to dive in. You may not need this script every day, but you'll be glad you have it when you do.