Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
Cotrio - The most beautiful way to move your brain and imagination
Standard Notes - A safe place for your notes, thoughts, and life's work
Akribian - Akribian turns children into Mathemagicians with their new iOS app, Count on me!
Joplin - 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, tagged and modified either from the applications directly or from your own text editor.
MathIsFun Times Table - Learn Your Multiplication Tables