Update: This offer is expired. You can find the current offer details here.
Up until last year American Express had a referral program whereby if you had one of their cards you could earn a referral bonus (usually about 5,000 points) for referring someone else to the card. For whatever reason they ended that program, though it looks like Chase is now getting in that game through January 31, 2014.
Meanwhile if you have a Chase Freedom Card you can now refer another person to the card, and if they get approved you get 5,000 points, up to a maximum of 50,000 points as well.
Best I can tell, as of now no other cards are offering a similar bonus.
Certainly a nice offering for anyone that has the card and wants to refer a friend or family member.