The Mozilla Foundation did it and set the official Guinness World Record for the most frequented software download within 24 hours.
Mozilla officially set a Guinness World Record with Firefox3.
According to spreadfirefox.com many users followed Mozilla's call and downloaded Firefox 3 on the release day. From 18:16 UTC on June 17th to 18:16 UTC on June 18th the web browser was downloaded 8,002,530 times.
Currently Firefox 3 was, all in all, downloaded 29,263,074 times. That equals 1,214.5 downloads per minute.