Longtime Mac developer Mark/Space, Inc. has just announced their first app for iPhone, and it's free.
Fliq (click opens iTunes) runs on the iPhone and iPod touch and is billed as a "real-time social networking app between friends in close proximity." If you and your friends are on the same Wi-Fi network, and if the free Fliq app is running on all of your iPhone or iPod touch devices, you can send contacts and photos to each other.
Upon launching Fliq, a list of nearby devices also running Fliq is displayed (see screenshot). After selecting who to Fliq information to, a screen prompts you to send your pre-selected "business card", another contact, or a photo to the other iPhone.
In practice, Fliq works very well. My wife and I were able to send photos and contact information back and forth with no issues. I'd like to see Bluetooth transfer capabilities built in for those situations where there's no nearby Wi-Fi network.
The Fliq Web page notes that Fliq will soon have the ability to transfer contacts and photos to a Mac or Windows PC.
In the interest of full disclosure, blogger Steve Sande has done consulting work for Mark/Space in the past, although not for this product.