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.
Google Opinion Rewards - Answer quick surveys and earn Google Play credits with Google Opinion Rewards.
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.
Receipt Hog - A fun and rewarding way to turn everyday shopping receipts into cash.
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.
FreeMyApps - FreeMyApps lets you get rewarded for watching cool videos, playing fun games, and trying new apps.