Green Card is n innovative service to share digital business cards. Simply create you card on your iphone and share it directly with your contacts. If you modify your card, all your contacts will be aware of it a minute after.
Sidenote: At the point of posting this program has been marked as beeing freely available without costs. As this program is hosted with the AppStore the status might change. Authors like to publish their programs for free for promotion purpose and then make it commercial. Also it could happen that the author decides to take the program down.