As related by George RR Martin on his Notablog, a number of SF fans and writers have begun a campaign to help into the research and treatment of Alzheimers. Terry Pratchett was diagnosed with the disease late last year and last week donated over half a million pounds (a million dollars) to the cause. SF writer Pat Cadigan has launched the official 'Match It For Pratchett' campaign, which aims to raise the same amount of money (or hopefully much more) for the study of the disease, which shockingly receives only 3% of the funds that cancer research does.
The official Match It For Pratchett website is located here. You can buy T-shirts with the profits going to the campaign here. You can directly contribute to the fund here, as long as you mention that it's part of the Match It For Pratchett campaign. Finally, GRRM has put up a number of rare, signed books for auction here, again with the proceeds going to the campaign.
The best of luck to those involved in the campaign, and best wishes to Terry Pratchett as he continues to fight this condition.