If Post-it notes are your reminder of choice, this one's for you. Use a finger to scribble on those familiar squares and the app pins them up (iOS users get a virtual corkboard background). You can also type notes, of course, and remind yourself of their urgency with an alarm.
WIRED Sixteen note backgrounds in the iOS version. Use photos as reminders. Email or tweet notes.
TIRED You can't resize or rotate notes. Android users stuck with plain yellow.