Need a little social pressure to ensure you stick to your resolutions? Commitie lets you set goals in a range of categories, and then issues daily email reminders as well as sharing your progress with other members of the Commitie community.
Commitie was built by the team behind Memiary, a journal-keeping app we featured a couple of years ago. It has a similarly minimalist approach: you can set goals in a range of categories, and assign yourself "points" for completing them each day. Achieving set points levels unlocks "achievements" to help you stick to your task.
By default, everything you do will be made public, so make sure to click the "Don't share any of my activity" button when signing up if you want your reminders to be more private. Commitie is free to use, requires a sign-in.