Letterspace is described as 'Taking notes made easy' and is an app in the Office & Productivity category. There are more than 50 alternatives to Letterspace for a variety of platforms, including Windows, Mac, Android, Online / Web-based and iPhone. The best alternative is Joplin, which is both free and Open Source. Other great apps like Letterspace are Standard Notes (Freemium, Open Source), Evernote (Freemium), Simplenote (Free, Open Source) and CherryTree (Free, Open Source).
Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, can be copied, tagged and modified either from the applications directly or from your own text editor.
Notational Velocity is a mouseless application for storing and retrieving notes. With Notational Velocity, searching for notes is not a separate action; rather, it is the primary interface. Searching encompasses all notes content and occurs instantly with each key pressed.