The Top 100 advertisers spend (month) a total of 49,045 million online ad dollars on this sites. Thereof
17,740 million USD on Facebook
7,217 million USD on IMdb
7,128 million USD on NYTimes
3,094 million USD on CNet
Lets look on Facebook

By far the largest advertiser on Facebook is AT&T, they spend about 30 % of their total online ad budget with Facebook
Lets look at the NYTimes

The NYTimes biggest spender is Sony, followed by News Corp. and International Herald Tribune.
via more at Permuto Discoveries
Target Markets: Ad Spending Across Four Benchmark Sites