Ken Kovash, over at the Metrics blog posts some significant information:

we’ve surpassed 60 million active daily users.

But Ken also links to a post by John Lilly dated January 2008, which mentioned that we had passed the 50 million active daily users[1].

If I read this right, we have gained 10 million active daily users in just 6 months, moving from 50 million to 60 million. Firefox has gained 20% active daily users in just 6 months, which is nothing short of amazing :-D

Now the Web is growing, but Firefox is growing faster that the Web itself, meaning that we're gaining market share in percentage. And wait 'til we ship Firefox 3: I'm betting that Firefox adoption will accelerate!

Notes

[1] For more details on market share, active daily users and active monthly users, please refer to John' post, Mozilla & Firefox market share.