FlyRig is a new website that lets you search rental listings in Manhattan only via a really nice Google Map mashup interface. The beautiful integration is something other real estate web developers should come by to admire. Not only does it display the listings from a query search as expected, but it allows users to search for other related things (say: dry-cleaners or gym) and plot their location in relation to the listed apartment. With this alone it is a much better alternative to Craig's List, and allows users to comment and rate listings - a feature remains to be seen. Cruising the site, I saw very little actual ratings or comments.
But there's more good stuff inside. For agents it has a super-easy interface to add listings for free. Moreover it molds all the aggregated data into useful nuggets for agents, including agent ranking lists, average rents by neighborhood, broken out over time, and a New York real estate specific news aggregation page.
Nice work. I wish I had it so good when I first went apartment hunting in Manhattan!