Suggestions for a good calendar / to do app for an iPhone?

I’ve been playing around with the calendar and tasks that come pre-loaded on the iPhone, and I wondered if there are any other options around? I used to use a Palm and found it more intuitive - just wondering if there’s anything similar for the iPhone?

I like 2Do, its on version 2.6 now. I think they have a free trial version as well. Its fully functional it just has limits on how far you can organize your tasks.

I liked it as it was easy to group stuff the way I wanted. And, for me, it “just worked”.

I like Calengoo. The main appeal to me is that it synchronizes with both GCal and with Google tasks (the task list in your email), which is my preferred way to track tasks on my computer.

DejaOffice claims to be putting out a product for newer smartphones (Android and iOS) that does synching with MS Outlook the way Palm OS did.

I’ve no experience with their product, but came across it while researching options just a couple of nights ago. Reviews seem to be a mixed bag, but apparently they are releasing new versions pretty often.

I currently use a Palm Centro largely because I like the seamless Office synchronization for the PIM stuff so much, and am dreading switching because from what I can gather nothing current really supports this. I’ve got my eye on the iPhone and I’m hopeful that these DejaOffice guys can produce something that works.

I’m a fan of Pocket Informant. It has a lot of flexibility in color-coding tasks, tagging them with map locations, setting alarms, and customizing the display. I used to use Palm for many years, but it’s been so long since I’ve used it that I don’t know how close it is to the old calendar, sorry.

iOS 5.0 has something along this line built in. It comes out October 12, I think. Probably worth waiting a bit and testing out though, if your alternatives aren’t free.

Personally I’ve been using Zenbe lists, which is free and very simple, but probably doesn’t have the features you want.