iOS: iCal is great, but when it comes to giving you an easy way to glance at all of your appointments at once, add new ones, and edit existing ones, it leaves a bit to be desired. Easy Calendar on the other hand, makes the process easy, and gives you a single-week view so you're always aware of where you should be next.
While Easy Calendar isn't as elegant and minimalistic as previously mentioned Agenda, it's very functional and is built to let you quickly add, edit and manage your calendar appointments. It syncs completely with iCal, so you don't have to manage two separate calendars. Easy Calendar is on sale now for $0.99 in the iTunes App Store, but that sale ends today, so if you want to try it, now is a good time.