Spread Firefox announced today the start of Firefox Download Day, which aims to get as many people as possible to download Firefox 3 the day it is released in its final form, most likely in June.
There is no precedent for a Guinness certified number of downloads, so the goal here is to set the bar really high to make it last, and grab enough interest that it may be included in the Guinness Book of Records.
You can help by just downloading Firefox 3 on the release day (if you do it from the Firefox Download Day page you will get a custom certificate). If you have a web site, you can help raise awareness by adding one of the many buttons and banners available in English, Spanish, Italian, French, Japanese, German, Polish, Portuguese, Russian and Chinese.
For added fun you can pledge to participate in Firefox Download Day and see which country gets the most fans on board.
Read the Firefox Download Day FAQ for more details.