Microsoft To-Do - Task management tool
Send to Things - Add tasks to Things from your Android device
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
NOW UI kit by InVision - A beautiful cross-platform UI kit (PSD & Sketch)
doo - A smart, simple app for reminders and to-dos
Elements for Sketch - High-quality UI Kits in Sketch, for free