I like keeping my tasks on a piece of paper right in front of me on my desk because I can see at any time what needs to be completed. The paper keeps all of my tasks top of mind and I've found that it helps me get the tasks completed. Every couple of days I move to a new piece of paper after the current piece of paper has most of the items scratched out.
Bragger noted that he decided to create Done.io after he too used primitive methods for managing his to-do task list. The service is amazingly simple. After creating an account, you add tasks to your to-do list. When an item is complete, you check it off and it gets crossed off your list. You can also "shift" an item which basically moves the item to a to-do later list. Shifted items return to your main list the following day. This helps you prioritize tasks at the beginning of each day.
Most of the to-do/task management apps are free and typically use the app to promote other apps and services. Remember The Milk offers a premium option for $25/year and Ta-da Lists promotes other 37 Signals products.
In addition, Done.io and several of the others offer APIs which allow developers to build on top of the applications. For example, you could create a program that would allow you to write and read your tasks from Done.io.
For now I think I will stick to my current task management system. As my startup grows and I hire more team members, I will certainly move to a dedicated task management system so that all members of the team can see what we are working on. What tools do you use for task and to-do management? Leave your methods and applications in the comments.