You're right in that the Standard model is pretty basic, you won't get many of the options available on the sport.
The sport also comes with slightly different bumper, a hood scoop, and run flat tires. Because of the run flat tires, it doesn't come with the Spare Tire that the Standard and Limited have.
It also comes standard with 18 inch wheels that are a different style that you can only get with the Sport.
You can compare them directly here.
http://www.toyota.com/rav4/features.html