There is a link for the Amex Platinum card offering a sign up bonus of 100,000 Membership Rewards with a reasonable amount of minimum spend ($3,000 in 3 months). The link shows up for everyone and you do not have to be targeted to apply. If you have your eye on an American Express Platinum card and have not had this version before, now is a great time to apply.
The official sign up bonus for the Amex Platinum card on the American Express website is only 40,000 so this is obviously a much much better offer. Update: The sign up bonus is now 60,000. See bottom of post on how to find the 100K sign up bonus.
If you are interested in the Amex Platinum card but this is not the right time to apply, you might still be able to find links offering an 100,000 sign up bonus at another time. Some people receive targeted offers of 100,000 all the time so for them this might not be a big deal. There are sometimes nontargeted links with an 100K sign up bonus found online but they are hit or miss and you have to use an incognito browser (sometimes with multiple attempts) to get these offers to show up. Another option, which I took advantage of last year, is to wait for a sign up bonus on the Ameriprise version of the Amex Platinum with no annual fee for the first year but there is no guarantee it will come back.
I am really tempted to apply especially since the minimum spending requirement is so reasonable but I don’t think the $450 annual fee is worth it for me at this time (even taking into account the airline free credits). I am hoping that a good Ameriprise Amex Platinum sign up bonus with no annual fee shows up again and have one of my parents apply and add me as an authorized user. I might still apply for the regular Amex Platinum card in a few years, when it is time for me to renew Global Entry and take advantage of the Global Entry fee credit. Even though the annual fee is steep at $450, it would be offset by the $200 airline fee credits per calendar year plus the Global Entry free credit.
Update: The link is no longer working. Here are some options for those that want to apply for an Amex Platinum card:
1) Hope to get targeted either by mail or check Cardmatch for 100K.
2) You might be able to find 100K by searching in incognito browser for American Express here.
3) Here is a link offering 75K points (open in incognito browser).
4) Apply for the no-fee Ameriprise version of the Amex Platinum. There is no sign up bonus right now (in 2015 Amex briefly offered a 25,000 sign up bonus) but there is no annual fee for the first year so you get to enjoy the benefits of the Platinum card without paying a fee for one year.
5) Apply for the public offer which has been increased to 60,000 points.