"You can use Google Keep to create, share, and collaborate notes quickly and easily. Since Google Keep syncs to Google, notes are accessible to you and anyone you share them with virtually anywhere: on your Android phone, tablet, and Android wearable, through a Chrome app, and on the web." If you are a Google user, this is the one for you.
Same as Google Keep but not on the Google interface. This has actually been around longer than Google Keep.
The interface is also very smooth and easy to use. "Wunderlist is the easiest way to get stuff done. Whether you’re organizing your work, sharing a shopping list with a loved one or planning an overseas adventure, Wunderlist is here to help you accomplish more."