If you thought street food was too elusive to track down, then get ahold of San Francisco's latest pretty young thing: the underground farmers market. The idea was first introduced to San Francisco last December by Iso Rabins of wild foods community ForageSF. Frustrated with his inability to get a booth at the city's established farmers markets, Rabins organized a private local foods fair — publicized only by word of mouth — that didn't require artisan vendors to obtain permits from the city's health department. The concept turned out to be a hit with the community. It's only been six months and ForageSF has already held three underground markets, including one that took place this week, with twice as many vendors and three times as much turnout. After eating my way through the prepared foods portion of the market, I caught sight of the line, which had grown to as long as a city block — a reminder that the early bird gets the worm. See what I filled up on when you keep reading.