Facebook has more than 500m Users (Full stats)

"People on Facebook
More than 500 million active users
50% of our active users log on to Facebook in any given day
Average user has 130 friends
People spend over 700 billion minutes per month on Facebook

Activity on Facebook
There are over 900 million objects that people interact with (pages, groups, events and community pages)
Average user is connected to 80 community pages, groups and events
Average user creates 90 pieces of content each month
More than 30 billion pieces of content (web links, news stories, blog posts, notes, photo albums, etc.) shared each month.

Global Reach
More than 70 translations available on the site
About 70% of Facebook users are outside the United States
Over 300,000 users helped translate the site through the translations application

Platform
More than one million developers and entrepreneurs from more than 180 countries
Every month, more than 70% of Facebook users engage with Platform applications
More than 550,000 active applications currently on Facebook Platform
More than one million websites have integrated with Facebook Platform
More than 150 million people engage with Facebook on external websites every month
Two-thirds of comScore’s U.S. Top 100 websites and half of comScore’s Global Top 100 websites have integrated with Facebook

Mobile
There are more than 150 million active users currently accessing Facebook through their mobile devices.
People that use Facebook on their mobile devices are twice as active on Facebook than non-mobile users.
There are more than 200 mobile operators in 60 countries working to deploy and promote Facebook mobile products"
Source:  Official Facebook Statistics, retrieved 18th August 2010.
Earlier figures here