Here are a few of the apps out there:
http://www.wedding.eversnapapp.com (this has a list of our packages with our premium features) - we also have a free version without instruction cards, Professional Photoretouching & Moderation for a Live Slideshow to have running at your wedding (like a live stream)
You can get the free version from http://eversnapapp.com or by just downloading the Eversnap app from the App store or Google Play Store
For the universal wedding registry (gifts from anywhere you want) - http://weddingscan.com/
Items for the house are great, but so is the ability to have your guests contribute to your dream vacation or honeymoon via a wedding registry site.
wedding planning -
http://evernote.com (keeps you organized and allows collaborative planning with your friends and family)
Have shared notebooks, so you both have access to contracts with vendors, travel itineraries, guest lists, etc. - very helpful when you're having tons of meetings with your numerous vendors
Not an app but pretty cool site that let's you coordinate bridesmaid dress shopping with your girls:
And if you have small tasks you need a few more hands to help you out with, why not try an app like http://Taskrabbit.com - As the wedding gets closer, have some people in your area help you complete some errands to help you achieve piece of mind.
At the end of the day, apps are cool, but no need to just download a ton of apps if they're not solving a problem. The best apps are the ones that solve the problem you're trying to solve or make your life a little bit easier in planning, organizing, collecting photos, etc.