SocialCard lets you easily share your phone number with a nearby friend.
Just open the app, and other nearby SocialCard users will appear. Select any people who you want to exchange phone numbers with, and just wait for them to select you back.
You can also send your contact info to people not using SocialCard. Enter their name and number to add their info, and you will be able to send them a text with your info attached and invite them to SocialCard.