SpeakerClock ($0.99) provides a bright easy-to-read display showing you exactly how much time you have left to present your paper and take questions. It's a deceptively simple application full of lovely little design touches. I used it at a recent conference and found it an absolutely valuable tool to have around.
This app works well both on the iPhone and the iPad -- as a conference organizer, it's really great to use the iPad's larger screen from across the room. As a speaker, the iPhone version works particularly well when placed on a small business card stand on the speaker's podium.
Want to easily share your contact information? Contxts offers a simple solution. You can sign up for a free account at contxts.com, where you can enter your details. Anyone with a phone (it doesn't have to be an iPhone) and an SMS plan can text a short phrase (like "demotuaw") to 50500 and they'll receive the information you set up at their website. Their free iPhone app lets you edit that information directly. What's more, when you turn the iPhone on its side, you can display a "HELLO my name is" contact sheet that instructs people how to retrieve your contact data. What's great about Contxts is that it's a solution that works with any group of people, whether they've hopped onto the Apple iPhone train or not (of course, if they have an iPhone or an Android phone, there's always Bump).
You can easily share your contacts with Mover+ ($1.99) as well, but there's a lot more you can do with this terrific application -- especially when you're at conferences. Mover+ lets you slide files and images from one iPhone to another, using ad-hoc Bluetooth networking. That means you can transfer data even when a conference's WiFi service is lacking, a situation that happens far too often in my sad experience. What's more, the user experience on this app is really slick (I believe it's been featured in an Apple commercial). If you like using apps that make people suddenly want to go out and buy an iPhone, this is one of them. Both users must have the app installed on their devices.
Need to track data while you're at your conference? Dayta ($1.99) is a sweet little app that lets you store pretty much any kind of structured information. Doesn't matter if you're logging miles walked, drinks consumed, food eaten, money spent, or hands shook. Dayta allows you to organize that information using free-form data logs -- and you can even graph that data. I really like Dayta's ability to adapt itself to multiple use-cases, an especially great feature for when you're traveling.
Solve (free) offers a really cute way of doing math on the go. Want to calculate a tip or split a tab? Sure, you can use a standard tipping app, or you can pull out Solve and use its handwriting interpretation to do the same tasks on a standard calculator -- by writing with your fingers. It's a lot of fun, which is kind of the point when you're out with people at a conference and you want to just show off your iPhone to others.