Hyperlocal Media just launched a beta version of Until Monday for the Brooklyn market. Until Monday does a paticularly good job of combining rich functionality and content in a playful Ajax UI.
From the press release: "Popular blogger and Six Apart Vice President, Anil Dash said of Until Monday, 'It's a beautiful community-based events site that's as attractive as it is useful.' Mena Trott, Six Apart's President and Co-Founder, said, 'the user interface just feels good to click around in.'"
Hyperlocal is new to me, but they seem like a pretty neat company—check out the other products they have in queue.