This is probably the best to-do list manager I have ever seen. I have just started using it recently and it has turned out to be even better then I hoped. They call it an Online To Do List and Task Manager, I call it a savior. It really does organize all your details and it is very easy to manage and integrate into other Google Apps. I have tried other online programs and downloadable ones but nothing comes close to this, they kept it simple with lots of features.

• Manage Tasks from any computer or mobile
• Get email, SMS, or IM Reminders (SMS for US only)
• Share your tasks
• Access from your phone
• Manage Tasks offline
• Use with Google Calendar
• Add task from iGoogle
• Its Free 

I try to organize everything in my head, but sometimes I do forget things and this makes things a lot easier. I have used it for a few days and it does keep all the information for me to remember.

Link: RememberTheMilk