Mozilla announced it set a new Guinness World Record for the largest number of software downloads in 24 hours.
The record-setting 8,002,530 downloads of Firefox 3 on download day have now been officially declared a Guinness World Record.

"The enthusiasm and creativity of Firefox fans was instrumental in achieving this record," said Paul Kim, VP of Marketing at Mozilla. "Our community members came together and not only spread the word, but also took the initiative to help mobilize millions of people to demonstrate their belief that Firefox gives people the best possible online experience."
"As the arbiter and recorder of the world's amazing facts, Guinness World Records is pleased to add Mozilla's achievement to our archives," said Gareth Deaves, Records Manager for Guinness World Records. "Mobilizing over 8 million internet users within 24 hours is an extremely impressive accomplishment and we would like to congratulate the Mozilla community for their hard work and dedication."
More details on the Spread Firefox site.