I was surfing the web as I usually do, and came across the name "ReminderFox" and a few positive comments. I installed, and quickly forgot about the extension. About a week ago I was looking for a online to-do list application, Geoff suggested many, but I already have to many organizational websites. I looked in my browser status bar and there was the answer; ReminderFox.
ReminderFox is very clean and simple to use, leaving a list of tasks in the task bar and prompting you a set time before the event. You can use it to remind you to do something or as a to-do list.
It's very useful if you already use FireFox to organize yourself, through websites such as Google Calender or GradeFix.