Niche listers: Many similar sites concentrate in a single aspect of the vacation rental marketplace. Quite a few are based in their destinations areas rather than the U.S. and many quote prices in euros or pounds:
What you get: Regardless of size, these listing sites share a common principle: They're facilitators, not agents. They just post the offers, availabilities, prices and such: Your actual deal is with the owner of each property. That's one of the reasons they offer the best prices: no agency markups, with listing fees low enough that many property owners list on multiple sites.
Typically, the large U.S.-based sites allow you to zero in quickly on what you want: price range, location, numbers of bedrooms and baths, swimming pools and other important facilities, communications, parking, accessibility, pet acceptance, availability and cost of housekeeping, and such. With many, however, you have to do a lot of trial and error before finding what you want.
One minor annoyance: For some reason, many of the listing sites include a few B&Bs. There's nothing wrong with B&Bs, of course, but they shouldn't clutter up the vacation rental displays.
The risk: The main risk with a listing site is that you see only what the owner decides you should see. Wide-angle lenses can make a closet look spacious and a good writer can make a cottage three blocks from the ocean to sound like the waves will break over the front balcony. You generally have to pay in full or make a big deposit in advance—often many months in advance—with a really big cancellation fee if you decide you don't like the rental after you arrive. And if you encounter a problem, you have to settle it with the owner, who may or may not be readily responsive or even available.
These days, most big sites mitigate this risk by posting renter reviews and possibly offering some sort of guarantee. Several sites de-list properties with a record of multiple complaints.
Agencies—the Safe Alternative
The other main branch of the marketplace consists of rental agencies that inspect the properties they list—some even manage them. Typically, they handle far fewer locations than even the midsize listing sites.