The program (or programs) that fit this bill, are Producteev and Astrid. These are two programs but they work together as a great task/to-do management system. I have spent hours researching a task management system and this one by far brings the most features and the cleanest interface.
Producteev is a web based program at www.producteev.com, it uses a very colorful interface and is very flexible. The best way to use this is by using the GTD methodology by David Allen. If you are not familiar with the GTD methodology, and to get a walk through on how to use it with Producteev, check out this article here for more details.
Astrid is an Android app that has been out since the early days of Android. This means that it has been developed to be very stable and feature rich. The interface can be modified to light , dark or transparent so you have enough options there to make it visually pleasing.
The power of these systems are from the pairing of the two programs. The key to making this work for you is to get very familiar with the Producteev program, spend time setting it up, and sync the tasks with Astrid. This is a seamless process and makes your Android device your reminder for all of your tasks. When used properly, it can really make a difference in your productivity. I have used these programs for school and my business for the last four months and I have found that I am getting more done and wasting less time.
These are free programs so there is no excuse for not getting that long list of objectives done and putting more money in your pocket as a result!
GTD Methodology with Producteev
Getting Things Done by David Allen (Book)