Expedia

I’ve been using Orbitz for years. And Booking.com for lodging.

For car rentals, I use Atlas Choice (http://www.atlaschoice.us) whenever I can because they are by far the cheapest. Typically, all of the other websites through which you can arrange a rental are very close in price – but Atlas Choice is almost always way cheaper (like 30-40% cheaper in some cases). The caveat is that you have to pay in advance, you have no choice in the rental company (but it will be a national brand), and there are no refunds. And when you show up to pick up your car, they will try hard to sell you every kind of service under the sun – just say “No” until they stop asking. At first, I thought they were some fly-by-night operation because their prices were so much lower and the reviews were really bad. But then I realized they operate world-wide and almost all of the bad reviews were by people trying to rent cars in the middle of nowhere in some country that I’d never heard of. In the US, all rentals will be with Hertz, Enterprise, etc. – so you don’t have to worry about that. As for the low prices – I don’t know how they do it – but they do.