In 2004 the Bundesliga took an idea from Juventus and decided to allow clubs to display gold stars on their logos to indicate that they've won multiple championships since the Bundesliga was formed in 1962. Clubs can display one star if they've won three Bundesliga championships, two stars if they've won five, three stars if they've won ten. The honour is known as Verdiente Meistervereine.
Update 2007: The latest club to join the list is Vfb Stuttgart, their dramatic 2006-07 Championship victory means they have now won 3 titles.
The list of clubs who have officially been awarded stars is...
There's been quite a bit of controversy over the awards, particularly from the former East German clubs, who obviously haven't been in the Bundesliga since it started, and who thought they should be entitled to display stars relating to their East German championships. Dynamo Berlin even went as far as putting them on the shirts anyway, ignoring the official awards. The federation eventually decided that all pre-Bundesliga and East German champions could display a single star with the number of titles displayed inside it.