Choose where to live by asking locals about their neighborhood. Listen in on their conversations or jump in and ask their advice – from wherever you are.  That’s what Eric Wu promises renters with his online site that combines the online sharing and conversational powers of a wiki and Twitter. RentWiki. Get a feel of the neighborhood beyond what you see driving by.  How family-friendly is it, for example, if you have kids? Who else is moving in?  Why? What’s there to do nearby? Asking people who already live there enables you to get a better feel of the area. 

That is, if current residents feel motivated to spend time sharing their views and recommendations.  That’s the part of Wu’s business I don’t understand. Yet the site is user-friendly – and more power to him for being the first to try. Perhaps tie-ins with Yelp, outside.in and other local-based sites and services would draw more people who aren’t looking for a place to rent.

Clearly, such Twitter verticals are growing wildly popular. Why not start one to boost sales in a low-cost way? Or, more daringly, start a Twitter-based business? Here’s more stories to whet your appetite for the idea:

• WallHogs uses it to attract customers and turn their uploaded images

 into prints – over-sized vinyl wall hangings actually. Dell uses Twitter as a fast and low-cost way to sell discounted products. (Could you as well?)

• You could use it to create an instant, real-time straw poll or to research stocks at Stocktwits which “aggregates tweets from a group of Twitter users who are involved in trading and investment topics.” 

• Even golf club owners are haltingly tip toeing into social media by Twittering the media with press releases. (How did owners manage to abbreviate their releases to 140 characters?) Remarkably, Scott Beale used Twitter and other social media tools to fund his start-up.

• British baker Poke is tweeting customers to alert them when a fresh batch is out of the oven.

• Chris Savage trolls on Twitter to find people who need his private video sharing software.

As with all Wisdom of the Crowd-based ventures the value and profits you generate are dependent on the smarts and diversity of the participants.   Twitterers who figure out how to reward people for smart, active participation in their Twitter-based service represent the cream that will rise to the top of our attention.  Posterous has similar possibilities as a tool for entrepreneurs and for existing businesses and groups.  Watch it grow over the next six months.