Blood can be donated at the fire station in Weißkirchen (part of Oberursel) on Saturday, 26th December, 2015 between 1pm and 5pm. The fire station is located at Friedrich-Ludwig-Jahn-Strasse 2a.
To donate you must be healthy and between 18 and 68 years of age. If you have not donated before, then you must not be over 60. You must take some form of identification with you, such as a passport, that contains a photo.
You can read more about what then happens here (in German).