EDIT: Offer is dead, lasted 6 hours
My friend just let me know that the American Express Platinum card is now offering a huge sign up bonus of 100,000 Membership Rewards points after spending $3,000 in 3 months. The normal sign up bonus is only 40,000 points so this bonus is huge.
While this card has a hefty $450 annual fee not waived the first year, there are a few nice benefits that help to offset the annual fee. With the Platinum card you get free lounge access, Hilton Gold status, Starwood Preferred Guest Gold status, $200 yearly airline fee credit, and extra benefits such as Global Entry or TSA Precheck credit.
American Express has upgraded the card benefits by adding 5x points on flights booked directly with airlines or with AMEX Travel, 2x points on trips booked through AMEX, and 1 point per dollar spent on everything else.
You can apply for the AMEX Platinum card here. Note: the link works if you open "incognito" mode on your web browser. This offer comes around once in a while and it doesn't usually last long! Read more discussion about this card in the Reddit thread here.