Wide Angle Lens
I could say: Go buy the Kodak V705 and stop the class right here. It's not a cure all, you won't get professional pictures with it, but you'll improve your listing pictures greatly. There are on E-Bay for around $350. It is a point and shoot camera. It is a lousy camera for anything other than taking pictures of listings but it does do that better than any other point and shoot I know of.
The number one thing you can do to improve your pictures is get a camera that has a wide angle lens! If you do not use a wide-angle lens then you are simply taking pictures of the furniture. A good picture of an interior room should have the floor, the ceiling, and at least two walls.
If you simply can't get your hands on a camera that can take a wide angle picture than see if you can try and find "moments" in the house that depict a lifestyle. That would be some lit candles around the jacuzzi tub in the master bath. A shot of a cozy reader corner with a recliner next to the fireplace and a floor lamp.
A while back Kodak made a model called the V705. A pocket sized camera that had a wide angle lens. It was a horrible everyday camera but a great camera for real estate.
Lenses are expressed in focal lengths to indicate how wide a view they will create. A wide angle lens is generally considered anything less than 35mm but you really want to get around a 20mm focal length.
A 20mm focal length will show a good portion of any room. It also allows you to get closer to houses obscured by foliage or on steep hills.
Comparison of interior shots on Newsletter #2
Camera
The biggest limiting factor in taking pictures of any kind is your gear. If you don't have the right camera it's just not going to work. I recommend getting a Canon Digital Rebel or a Nikon D40. These types of cameras can be purchased used for a few hundred dollars. You can spend a couple of hundred dollars on a wide angle lens, and then a bit more on a flash that mounts to a "hotshoe" on top of the camera. This is referred to as a speedlight. So getting outfitted should be less than $1,000. After that you've only got to learn a few basic principals about photography. In the digital age you can keep shooting until you like what you see on the preview screen. A tripod & step ladder come in handy from time to time as well.
Point & Shoots
There are a good number of point and shoots that will do "stitching of images" and that can create a panorama but those types of images are much wider than a standard image. Typically they're a 6:2 aspect ratio instead of a 3:2.