San Francisco -- Hipmunk, the San Francisco-based developer of a travel search site that aims top simplify the process of online travel planning, said it has raised $15 million in its second round of funding, led by Institutional Venture Partners (IVP). Previous backer Ignition Partners also contributed to the round, which the company will use to hire more engineers, bolster business development and marketing activities and enhance its offerings. The company, which launched in mid-2010 out of Y Combinator and raised its first round in Feb. 2011, operates a visual travel search site. Flight results are presented in a visual "timeline," while hotel results are shown on a map. Todd Chaffee, a general partner at IVP, will join Hipmunk's board as its fourth member.