Dozens specialize in Europe or parts of Europe, the Caribbean, and Hawaii; many concentrate on a single country, and many on an individual region of a country or single city. France, the U.K., Italy, London, Paris, and Tuscany are especially well covered.
The main advantage of dealing with one of these agencies is that the agency has actually screened the properties. Staff can discuss each individual property with you, and can jointly assess whether it's right for your needs. Moreover, when you rent through one of these agencies, your deal is with the agency, not the property owner. And if you have a problem, the agency is on the hook to fix it.
This degree of security comes at a price. The agency has to charge enough markup to cover the cost of inspections and management. Although I've never seen the same property listed through both channels, I guess that an agency rental costs something like 20 percent more than one through a listing site.
I've rented through both listing and agency sites and I've been happy with both. Your choice is a matter of preference: Minimal cost through a listing site or minimum risk through an agency. Either way, you'll find more than enough options to provide a great vacation stay. Enjoy!
Ed Perkins is a contributing editor to SmarterTravel and a respected commentator on all aspects of the travel industry, including passenger comfort and rights, travel insurance, the best credit cards for travelers, and car rental fees. SmarterTravel provides expert, unbiased information on timely travel deals, the best value destinations, and money-saving travel tips.