This is Frugal Foodies, a Bay Area group that brings people together to cook and eat in community. Founded by J Moses Ceasar in 2005, Frugal Foodies has thrived since then in Berkeley and San Jose. Menus vary (according to the site's blog, a recent evening was an experiment in veganism) but are always vegetarian and mostly organic.
My friend Margaret went a couple weeks ago and came back glowing with great things to say about how it works and how much fun she had. I hope to try it soon and report back on another fun way to share food.