Chord Generator - this tool generates jazz chords (as many or few as you would like) in almost any possible format. It can be used to practice piano voicings, spelling chords, or as a jumping-off point for composition.
Habit Tracker - a tool to keep track of improvement and consistent practice of a skill you would like to learn, or a habit you would like to create. Simply set a goal, and each day that you practice or make a step towards this goal, mark off that day. Your only job is to not break the chain. Inspired by Seinfeld's productivity methodology.