The iTunes App Store is glutted with to-do lists and time managers, but many are so simple they're ineffective. Appigo's Todo is the highest cost of its cohort, but is also more complete than the budget offerings. Unlike other to-do lists, you can have Todo assign a due date and priority ranking; it will winningly associate tasks with mobile numbers and Web sites. You can further synchronize your lists with your pro Remember the Milk account and with Toodledo, both Web-based task organizers. Now if only Apple would let Todo take the extra leap and let loose with an alarm when a deadline nears.