[Update 9/5/2011] It is amazing that Amex hasn't pulled the old link (even though the landing page is fare gone) for more than a year - it is still up as of writing. What is more, Amex has just introduced a slightly better deal: get 50K after spending $5,000 within 3 months - the spending requirement has been reduced by $5K. The best deal on this card was of course the 1-day 75K deal that Amex ran several times in the past. But if you did miss one of those, this one is not shabby at all.
Landing page for the new 50K offer (expired)
Application page for the new 50K offer (expired)
[Original Post 8/29/11] Amex recently overhauled its Business Gold Card - now it has similar 3-2-1 earning structure like one of our favorite - Amex PR Gold Card. And what is even better is they are offering 50,000 points as the signup bonus (after spending $10K within 5 months) with the 1st year free ($175 saving). We will review the card pretty soon and the application page can be found here. Our review is up [11/20/2011].
[These may be far gone by now] There are also two widely reported Amex card offers - they are targeted but many people succeeded in being bumped into these offers. You can try your luck - sign up the cards through Amex website and after approval send security message to ask them apply Bonus ID to your account:
Amex Platinum Card 100,000 points ($450 annual fee not waived) targeted offer - Bonus ID 3882 or 5748
Amex Premier Rewards Gold Card 75,000 points (1st year free) targeted offer - Bonus ID 6661