After clicking the appropriate button, select which of your blogs you want to add the widget to, then click "Add widget". The Red Cross assures us that 100% of the money raised is going to disaster relief efforts in Haiti — we and they thank you for your support!
Not on Blogger? Be sure to visit the Red Cross's Haiti banners page with banners that you can add manually, or visit Google's page containing information about relief organizations, news and contact info relating to the earthquake.