When I was looking for a vacation rental in northern Michigan last summer, Airbnb pickings were surprisingly slim, but there were a wealth of places for let on sites such as VRBO and Homeaway. While it's easy to find a place for the weekend in Paris or Portland on Airbnb, not everyone with a beach home in Petoskey, Michigan, lists on the site. When I found a place, the rental process involved mailing checks for deposits and down payments, a far cry from Airbnb's credit card system.

To make the process of searching for the perfect spot a little easier, Tripping.com scours sites -- including VRBO and Homeaway -- for vacation home listings. Sometimes a weekend away is just not enough, and the site's focus is on helping users find a cabin or cabana for those weeklong stays.

The site aggregates over 5 million listings in 100,000 areas, and it just secured $16 million in funding. "Historically the way this would work is you'd find a vacation rental online, you'd email the host, and you'd show up with a check in hand," Tripping founder and CEO Jen O'Neal tells TechCrunch. "Now you can do all of that online, but on average a traveler will go to at least five sites to book a vacation home."

While you'd assume sites such as Airbnb have cornered the vacation rental market, the four main sites -- including Homeaway, Priceline, and TripAdvisor -- make up only 22 percent.

When I went searching for a place outside Petoskey for next summer, Tripping definitely picked up some places not listed on Airbnb. However, I still had to go to Homeaway or VRBO to book them. That means, if I chose the same place I stayed last year, I'd still be mailing a check to secure my spot for the weekend.