Here's a link to a TechCrunch article analyzing the amendment in great detail:
http://techcrunch.com/2012/03/07/facebook-amended-s-1/
Venture capital investors in Facebook include Accel Partners, Andreessen Horowitz, Elevation Partners, Founders Fund, Greylock Partners, Kleiner Perkins Caufield & Byers, Meritech Capital Partners, Millennium Technology Value Partners and Technology Crossover Ventures.
Here's a link to the recent amendment to the registration statement: http://www.sec.gov/Archives/edgar/data/1326801/000119312512101422/d287954ds1a.htm
Here's a link to the original registration statement: http://www.sec.gov/Archives/edgar/data/1326801/000119312512034517/d287954ds1.htm
Here are links to prior posts on Facebook:
http://www.allenlatta.com/1/post/2012/02/facebook-files-for-ipo.html