I got a chance to get a quick preview and overview of Vast.com yesterday. What is Vast? On first blush it’s yet another free classifieds site, joining an already extremely crowded field. But if one looks closer it’s much more interesting than that.

Naval Ravikant, the CEO and founder — he also founded Epinions.com — doesn’t want to be a consumer destination and says, "I won’t spend a dime on marketing." Like Edgeio, Vast can "pick up" listings from blogs but it also obtains data from the large aggregators (e.g., Cars.com, CareerBuilder) and — this is critical, according to Ravikant — the "vast" middle range of sites (e.g., individual Realtor sites) whose content typically doesn’t make it into conventional aggregators’ listings.

Ravikant called this realm "the middle tail." But you shouldn’t think about Vast as a classifieds site. Think of it as a vertical-local search site. More categories, beyond typical classifieds, will be rolled out in the near future.

The entire site is based on crawling, with dynamically generated and contextually relevant navigation. Here’s an example of Audis in my ZIP code. What Vast, as well as sites like Openlist.com, start to show is that crawling can create structure out of unstructured Web content. This makes potentially possible a whole new generation of local search sites.

Ravikant has a monetization stategy based on premium placement. But he says he has a long time horizon and a slow burn rate. Beyond the crawling strategy, which isn’t yet perfected Ravikant admits, the really interesting thing is what you can do with Vast’s API. It allows anyone — whether a blogger or a large publisher — to take a vertical index and plug it into a Web site. That would include the monetization when it kicks in.

That means, say, as an individual Realtor (assuming I had the chops to implement) that I could list all the homes for sale in my territory or a larger geography by tapping into Vast’s API. Vast makes huge amounts of content immediately available, either horizontally or vertically, to anyone who wants to publish that content.

Vast will be a site and a company to watch both for its technology and capabilities, as well as it’s "attitude." There’s more to say, as always …

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Per John Battelle . . . a classifieds roundup by Gary Price of Ask (formerly SEW).

More on Vast from Paul Kedrosky.