A while back, Google launched a Tasks lab for Gmail. Now they have added a new tasks feature for Google Calendar after many requests for one.
There is now a "tasks" link in the upper right-hand corner of the Google Calendar page. Once you click on it, a box will come up on the opposite side of the screen, where you can add tasks in list form. They come with checkboxes so you can check them off as you accomplish them, and a form to enter a due date. The task will then appear on your calendar on the day it is due.