Uploading things through the "Choose File" prompt on the web is slow and cumbersome. Google Chrome, however, lets you drag and drop files into any window to upload them, even when it isn't a feature of the webapp you're using.
We're not sure when Google added this feature to Chrome, but it is incredibly handy—no longer do you have to browse for files when you upload them. Just drag a file from your desktop onto the "Choose File" prompt and it will automatically add it for you. It's incredibly simple, but a nice time saver.