Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
Springtomize - Tear down the walls
TaskPaper - Plain text to-do lists for Mac
Winterboard - Give your iPhone or iPod Touch a graphical overhaul!
Microsoft To-Do - Task management tool
Dreamboard - DreamBoard lets you take control over the homescreen of your jailbroken iPhone.