Business card scanning software is nothing new in the App Store. There are plenty of apps that take data from a picture of a business card, but none that get the data right every time. Sometimes shadows get in the way, or the app thinks that the name Chris looks like Cheryl, and boy is that annoying.
TechCrunch talked about how CardMunch does things a bit differently, adding a human element to the card scan. Like other card scanning apps, it still captures the card image with your iPhone's camera, but then the picture is sent off to the CardMunch office where real humans extrapolate the data. Real humans that guarantee 100% accuracy! Once it's done, the data is sent directly to your Address Book or to the CardMunch app itself if you don't want to clutter your contacts.
The service does cost $0.25 per card, but if you have to scan 400 cards, CardMunch claims that you will save an average of 23 hours of data entry time. Seems worth it to me. Try the app out for free and get 5 free card scans with your "purchase".