I've always been struggling with multiple applications to maintain a calendar and todo list. Those that combine these in a single app always come across to me as mentally strenuous with a billion features rather than streamline my thoughts.
Above it all, I've always wanted to sync it with the web so that I'm device independent.
After trying numerous applications, I chanced upon 2do for iPad. It separates the categories which I created with the toodledo web service into multicolored tabs, which i found to be very graphically intuitive.
Secondly, each tab comes with it's own calendar, and tasks without a due date will not be reflected on the calendar.
The deal breaker about this app for me is that it allows you to add jpgs and notes to a task. Now here comes the customisation bit. Other than my individual project categories, I created a 'calendar' category, and how it works is that every appointment will be a task with a due date, so that it gets shown on the calendar. I can then add screencapped maps, sketches and notes from other apps as a call out thumbnail for reference.
Next, I created a 'notes' category, so I can do just like the above, except that I won't have a date attached to it. Random thoughts, song lyrics, interesting websites, doodles, recipes and miscellaneous meeting notes are all added there, like a repository for general notes.
Best of all, these can be synced back through toodledo, and over to my iPhone, or the PC, only glitch is that the pics don't get synced.