This is the 25 May offer in commemoration of AAdvantage's 30th Anniversary.

In conjunction with the United Service Organizations (USO) and Susan G. Komen for the Cure, you can get 30 AA miles per dollar you contribute through special links. Contributions must be made between 25 May and 31 May through special links.

Here's the link to the promotion (which gives you links to Komen and USO for donations).

Annual limit of 50,000 AA miles for USO donations and 50,000 miles for Komen

P.S. I realize this is AA-centric, but it should be posted here so others who don't always check the AA forum but do collect AA miles would be more likely to see it before it expires.