18. Let Drive sign on the dotted line
If you find yourself needing to sign a lot of electronic documents, a Drive-connected app called HelloSign, made by the same folks behind HelloFax, can be a tremendous asset in your cloud-based arsenal.
Once you've installed the HelloSign Chrome app and uploaded a signature, all you do is right-click any file in Drive and select to open it with HelloSign. You'll then be able to drag and drop your saved signature wherever you want in the document and save it or even email it to someone right there.
The self-signing functionality of HelloSign is free and unlimited; if you want to use the app to request other people's signatures as well, pricing starts at about 12 bucks a month.