PostponeIt is a handy application that allows you to create reminders in a very easy and simple way. You can add a description to a reminder by either typing it or recording it via a microphone. In addition, you are shown a list of all your pending reminders, which you can edit. To make things easier, you can assign hotkeys to the your most-used actions.
The program does not offer any traditional user interface, but simply installs an icon in the system tray area. You can right-click on that icon to display a menu from where you can access all the functionality the program provides. And you can also double-click on that icon to open the "Add reminder" window.
When adding a new reminder, you can choose between two modes – fixed-time and countdown. If you select fixed-time, you will need to set the due date and time, while countdown will ask you to set the countdown time after which the reminder's alarm will go off.
As for reminders themselves, they show you a notification window with the reminder's title. This window offers you four options – three to delay the notification (for 5 minutes, 1 hour, or 1 day), and one to close the window and so delete the reminder altogether.
In general, PostponeIt provides a really easy way to create reminders, though I believe it lacks some key features, such as creating periodic reminders.