This post will be one of several on this theme, and it's unashamedly focused on Aussie pilots. Others may find it useful but the applications I talk about will be Australian. There's plenty of info on US applications elsewhere.
The first application I want to talk about is of the "you can't leave home without it" variety. In fact I think that's literally true if you have an iPhone. It's called NAIPS and its written by Rowan Williamson. Search for it on the App Store.
This application gives you access to most of the functionality of NAIPS on your iPhone. The interface is nice and clean and the application is fast and simple to use.
This is the main screen for a location briefing. All of the elements from this screen will be familiar to people who use the web version of NAIPS - except for the button labelled "Common". This is one of the great things about the app - it remembers where you've been and you can just click and load past locations. In just the same way as you can with NAIPS you can type in a location (YMML for instance) or a forecast area (30, 21 whatever) in each cell. When the briefing comes up you can choose to save it. Again a really nice piece of functionality that allows you to quickly access often used briefings. You will need your own username and password for NAIPS. This is free and simple from Airservices Australia.
When you retrieve the saved briefing you have the option of clicking the update button to get a current version of the saved briefing. The application does support sideways viewing so you can get the full width and bigger text. (What do they call that sideways viewing on the iPhone?)
There's lots more including an alternates briefing. But simply do yourself a favour and go and spend the $7.99 AUD. It will be the best money you've ever spent.
Rowan is working on the capability to submit flightplans from NAIPS. That will be absolutely the icing on the cake!
Footnote: I see from visiting Rowan's site that the first part of the flightplan submission functionality should be available any day and that there's some exciting new stuff with charts coming.