Keeping track of wedding expo contacts is much like keeping track of vendor contacts. I meet with many vendors, and keeping track of them can be tedious. One of the most dreaded tasks is imputing vendor contact info into my address book (iphone). Since most often I am inputting from a business card, much like you would from a wedding expo, I decided to find an app for scanning them in.
One app I tried and liked was Camcard by Intsig Information. It did a very nice job of capturing and converting the business card information, but the price was a bit high for my liking. My other recommendation is BizSnap which also converted the data efficiently. BizSnap is free and how can you argue with that.
The business cards are captured as an image and then converted to text. At that point they are opened for editing in case corrections or modifications need to be made. Once all the data is correct it can be saved to your contacts file. You might also want to tag each of the contacts with the wedding expo or the expo name so they can be found with the search feature at a later time.