Over the years, I have taken quite a few pictures of automobiles. I would like to use the photos to create several calendars and then sell these calendars online. Am I violating any law by using these pictures in the calendar? Do I need to get any type of permission from the owners?
Copyright law confers certain exclusive rights onto creators of original works. There is no doubt that, as the photographer of the cars, you own the copyright in any photos that you take, even if you never formally register them with the U.S. Copyright Office. Generally, you do not need the permission of the cars' owners, since the cars were presumably out in public.
Having said that, make sure your photographs do not also contain an image or work that is protectible under copyright law. For example, if there is a mural in the background, or if there is original artwork or imagery on one of the cars, you would need the artist's permission. Automobiles themselves are not typically protected under any sort of copyright, unless there is a special ornamental customization. The general rule is that customization that is functional cannot be protected.
In terms of the names of the cars, these can be used for informational purposes. However, you should not use the cars' logos or trademarks in the advertising, promotion, or cover of the calendar. Doing so could create consumer confusion by suggesting that your calendar is sponsored or affiliated with the auto companies. This exposes you to the potential for litigation by the car manufacturers who own those trademarks.
You should also make sure that you are not reproducing images of any people, particularly children, who might be sitting in the cars that you photographed. Doing so could implicate their right of publicity, and they might become angry and initiate litigation against you if they see their images being sold online without their consent.
As a matter of courtesy, it might be wise to seek the permission of the cars' owners, even if you are not required to do so under copyright law. This consent will prevent these owners from becoming surprised or angry when they see the calendar being sold. They might even be supportive, and offer you additional information about the cars, or interior shots that you might not otherwise get.