Task2Cloud is integrated with Android calendar GTD-style task manager.
✓ Supporting multiple accounts
✓ Seamless integration with android calendar
✓ Google calendar (web) synchronization
✓ Task2Cloud web application
✓ Unlimited tags
✓ Configurable trays
✓ Advanced event preview (with checkable subtasks)
✓ Advanced event editor
✓ Search events in tray and through all the events (without trays)
✓ Android ICS look and feel (actionbar, fragment layouts even in 2.2)
✓ All power of integration with Calendar: sms/email reminders, shared calendars and etc.
✓ Easy to use and multifunctional (you can use Task2Cloud as a task manager / todo list / shopping list)
✓ Completely free
You can use Task2Cloud web (beta): http://task2cloud.appspot.com.
I'll appreciate feedback, as it will motivate me to do Task2Cloud better! :)