For the simple interface you might want to check Workflowy (http://workflowy.com http://workflowy.com). Not sure if it can integrate with a calendar. I use Day

For the simple interface you might want to check Workflowy (http://workflowy.com http://workflowy.com). Not sure if it can integrate with a calendar. I use Daylite. A bit heavy sometimes and the learning curve is steep, but once you get the hang of it, is fantastic.