Adam Goldstein and Steve Huffman decided to do what Kayak already did: make a better travel search engine (but better). Hipmunk's clever interface hides itineraries with ugly connections and confusing codeshare flights. Huffman, a YC alum, sold his user-powered news aggregator, Reddit, to Condé Nast in 2006. "I figured we'd do this, it would flop and we could move on to something better," Huffman laughs. "But it's really working."
Top of the list! Nice job, team hipmunk!