Facebook has more than 750m active users (full stats)

"People on Facebook
More than 750 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
Entrepreneurs and developers from more than 190 countries build with Facebook Platform
People on Facebook install 20 million applications every day
Every month, more than 250 million people engage with Facebook on external websites
Since social plugins launched in April 2010, an average of 10,000 new websites integrate with Facebook every day
More than 2.5 million websites have integrated with Facebook, including over 80 of comScore's U.S. Top 100 websites and over half of comScore's Global Top 100 websites

Mobile
There are more than 250 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 1st September
750m active users announced in July (without full update)
Earlier figures here