When I first heard about rental startup Airbnb, I thought it sounded a bit odd — and finding out its founder rents rooms from his customers only increased that impression. But now I’m hearing more and more buzz about the company, and today it announced that it has raised $7.2 million from Sequoia Capital and Greylock Partners.

The company was founded as a way for people to rent out spare couches and rooms to travelers. In today’s press release, Airbnb says it’s now used to rent out much more, including castles and sailboats. The site includes 50,000 listings in more than 8,000 cities and 166 countries. People have used the site to book more than 700,000 nights.

Along with the funding news, Airbnb announced a new iPhone app and an Instant Book feature. The iPhone app allows users to browse and book properties on their phone and includes a “Find a Place Tonight” option that lists available rooms near your current location.

The Instant Book feature lets hosts say that they don’t need to approve a reservation, so guests can make their reservation with just a click. In some cases, that might not be anything more than a nice convenience, but it could be a lifesaver if you’re trying to find and reserve a room at the last minute.

Airbnb was incubated by Y Combinator and also raised seed funding from Sequoia and Youniversity Ventures. Its total funding is now $7.8 million.

[via Business Insider]