AOL Classifieds, which launches today in the US and Canada, allows sellers to post listings free, just as Craigslist does. (The service makes money from selling increased-visibility ads, sort of the way eBay makes money from the featured-auction option.) A UK version of the service will launch in the near future.

The service is powered by Oodle and aggregates listings from over 80,000 sources and 250 partner sites, many of them intensely local in orientation. Higher-profile members of the Oodle network include the Washington Post Express, Military.com Classified, MySpace Classifieds, Etsy, LiveDeal, and Local.com Classifieds.

To no one's surprise, AOL Classifieds listings will also combine listings from services on AOL that already offer classified ads, including AOL Autos, AOL Jobs, AOL Personals, and AOL Real Estate.

Fancy stuff, though one suspects that fear levels at Craigslist today are sub-critical -- as least where sheer volume is concerned.

A few searches for comparison's sake revealed interesting differences between the two. For instance, we searched on "kitten," a time-sensitive commodity and one offered by a wide variety of vendors. AOL Classifieds delivered 91 Seattle-area results to Craigslist's 48, but some AOL ads for specific kittens went back as far as three months -- a long time when speaking of young cats. The oldest Craigslist results, on the other hand, were posted a week ago. (We did not, however, need to read the post about the kitten-eating cat; Craigslist is big, but no one ever accused it of being focused.)

The AOL offering, however, is impressive in other ways. Search results included photos and brief descriptions, and many of the ads we saw were from PetFinder.com, which works with the local Humane Society to list available animals. Those listings and some others were marked in the search results with a "trusted listing" badge, which according to the site means that "AOL Classifieds believes this listing can be trusted based on the site's fraud protection and customer policies."