Here is the current Wikipedia report card:

Worldwide unique monthly visitors: 475 million. (North America: 99 million)

Worldwide monthly pageviews: 19.1 billion. (English: 9.2 billion)

Mobile monthly pageviews: 2.4 billion. (English: 1.3 billion)

In November 2012, here are the Wikipedia statistics that stand out:

Number of content pages: 4.1 million. (total pages: 28.8 million)

Number of administrators: 1453. (total editors: 78k)

Monthly Active Users: 134k. (registered users: 17.9mm)

According to Alexa, the only sites more popular than Wikipedia are Google, Facebook, YouTube, and Yahoo. The rest of the top 10 are Baidu, Live, Twitter, QQ, and Amazon.

Tumblr passed Wikipedia in pageviews in summer 2011:

In summer 2011, Tumblr had 41mm unique monthly visitors and 6.5 billion pageviews.

By comparison, Wikipedia had 423 million monthly visitors and 5.6 billion pageviews.

Feb 2012 report card suggests Wikipedia's numbers are now 475 million / 9.2 billion.

Tumblr has not hit 100 million monthly actives but it has 20 billion monthly pageviews.

The Dark Web is much, much bigger than Wikipedia and Tumblr.

Interesting link: World Internet Population.

Currently there are 2.276 billion Internet users with 12.833 billion monthly pageviews.