If you're an Evernote user, you already know why you need this app. If you're not an Evernote user, you're missing out on a powerful service that keeps your notes, pictures, and audio recordings organized and synced across every major operating system, desktop and mobile alike. An impressive optical-character-recognition software engine even catalogs and searches the text in pictures of your handwritten notes. The service is so flexible that you could run your entire business out of Evernote, tapping the service for everything from expense tracking to inventory management. Opting for a $45 yearly subscription ditches the ads and tosses in PDF search capabilities, note history options, and the ability to upload up to 1GB of data per month, among other things.