It's not clear why Google doesn't treat Google Tasks as a standalone service: it's integrated with Gmail, Google Calendar, there's an iGoogle gadget and a mobile version, but no standalone interface. The most recent update is that the iGoogle gadget has a canvas view that's displayed when you maximize the gadget.
The gadget lets you create multiple lists, use the toolbar to clear completed tasks or to reorder tasks, sort the tasks by due date and view a list of the completed tasks.
If you don't want to use iGoogle, the URL of the canvas view is https://mail.google.com/tasks/canvas. Bookmark the page and pretend it's the standalone version of Google Tasks.
Here's the full list of Google Tasks interfaces:
https://mail.google.com/tasks/m - mobile version
https://mail.google.com/tasks/android - Android version
https://mail.google.com/tasks/iphone - iPhone version
https://mail.google.com/tasks/ig - iGoogle gadget
https://mail.google.com/tasks/canvas - iGoogle gadget in canvas view
(replace /tasks/ with /tasks/a/your_domain/ for the Google Apps versions).