Venture Capital investors include Kleiner Perkins Caufield & Byers, Institutional Venture Partners, Foundry Group, Avalon Ventures and Union Square Ventures.
Links:
Bloomberg: http://www.bloomberg.com/news/2011-12-08/zynga-said-to-receive-enough-orders-to-cover-all-100-million-shares-in-ipo.html
Seeking Alpha: http://seekingalpha.com/article/312763-zynga-ready-to-skyrocket-out-of-the-gate
MarketWatch: http://www.marketwatch.com/story/zynga-jive-software-to-head-big-ipo-week-2011-12-08?link=MW_latest_news