SF-based Zynga, a new casual games startup targeting social networks, has raised a $10 million first round led by Union Square Ventures, reports NYT. Other backers include Foundry Group, Avalon, Peter Thiel, Reid Hoffman and Bob Pittman. Zynga, founded by veteran entrepreneur Mark Pincus (Tribe.net, SupportSoft), has developed a portfolio of casual games specifically made for play on social networks, such as Facebook and MySpace. The games themselves — classics like poker, blackjack and Battleship — have plenty of competition on these sites, but it’s hoping to exploit the social networking environment to a greater degree than others have. The company, which makes money selling links and helping other developers get users, claims to already be breakeven. USV partner Fred Wilson discusses the investment at the firm’s blog.