Marlene Dietrich - The "official" site for the German-born actress is great-looking and filled with information. It has the blessings of her family, too.
Marlene Dietrich - From The German-Hollywood Connection, a site devoted to German influences on classic filmmaking.
Marlene Dietrich: Legend - An elegantly-designed site devoted to Marlene Dietrich's concert career and appearances on TV. Liberally sprinkled with photos and quotes from her autobiography.
UL's Marlene Dietrich Collector's Page - A very nice-looking site that features hundreds of photographs of collectible items, from books and posters to records and wearables. In English or German.
Marlene Dietrich: Woman and Legend - A beautifully-designed site by Alexandra Rattay, with a lot of quotes, articles, and other information, all designed so that there's no scrolling necessary.