2Do is a productivity app which helps you stay more organized when working between OS X and iOS. 2Do has a very easy-to-use interface and allows you to create smart lists, filter tasks and even drag and drop email links into 2Do. You can sync with multiple Macs via Dropbox, Reminders (CalDAV), Toodledo or iCal CalDAV Server. However, iCloud is not included as a syncing option which may be a problem for those that use it for most of their OS X syncing tasks.