Keep your New Years' resolutions with Joe's Goals (and do other stuff)
An app I've been using on and off for a while is Joe's Goals, which is a goal tracking application designed to motivate you and help you visualize and accomplish your goals. You can create a list of goals like "Drink at least 0.5L of water instead of Coke", "Write at least 2 posts a day", and you can they mark a goal done. You get a point value for each day based on the goals you have completed, all shown in a very simple, but sleek interface.
The beauty of this app is that it is simple on the surface, but once you think about it and see some advanced options (there aren't a lot) you realize that this is more than an app created in 3 minutes to satisfy the armada of New Years resolution people. There are actually two types of goals available, positive and negative. Fulfilling a negative goal will give you a negative score, while a positive will give you a positive score. You can also fulfill (or tick) a goal more than once a day. For the goal "Write posts" you can award yourself with as many ticks as the posts you write for example.
The picture is further shaded by the fact that you can add a weight to each goal, so publishing 2 posts a day (two ticks) would raise your points, but drinking even one can of Coke could decrease it by much more, it's all up to you. There are a few more features in there, but in simplicity lies the key here, just set up your goals, visit it once a day and keep ticking. After a while you can see how you're doing, getting a higher score for me is motivation to drop that Coke can!