Do It Tomorrow is a simple app available through the web for free or as an app for iPhone (free), Android (free) or iPad ($4.99). The look of the app is distinctively notebook-y which is what first attracted my attention. You can add a to-do item and then shoot over to tomorrow if you can’t get it done today. And that’s about it.
The iPad app will sync with iPhone and web allowing your simple 2-day-at-a-time planning to go with you wherever. While its limited functionality does not allow for long term planning, it can help keep track of just those things you need to do today. Of course, a pocket notebook will do the same thing.