Ewidi basically consists of searching and publishing. You need to buy a used car in San Francisco, you either search for it, or browse tags/categories/locations for text messages corresponding with the subject. On the other hand, if you're an unemployed coder in need of work in Amsterdam, you'll post a message saying just that.
It is an internationally-oriented (the whole service is translated to 27 languages), service, and many users might find it odd that ads are not all in English. But why should they be? You can filter only the ones that you're interested in, and if someone needs to post information that will be of interest to anyone, no matter at which location' they're based, they'll probably post in English.
Ewidi also allows for creation of sub-domains, which correspond with tags/certain interest groups. Some of the ones that are available at the moment are film.ewidi.com, macedonia.ewidi.com, and osijek.ewidi.com (Osijek is a city in Croatia; it's no wonder they chose it because one of the authors of the service, Marko Kovač, is from Croatia.).
After you register, you are able to publish your own messages and to interact with other users. The registration doesn't even require an email, so it's really simple to try, but I personally like when at least an email is required to register for a service, because it keeps spammers at bay.
Unfortunately, currently by far the best way to use the service is by using search - the categories and tags aren't really well established yet. But, judging from the swarm of Spaniards which are currently overwhelming the service (the story about Ewidi has been published in the Spanish magazine El Mundo), the idea is working well in its current state. Looking forward to see how this one will develop.