Need help getting 'toned' but not 'muscular'?

I'm trying to lose between 10 and 15 pounds over then next 2 or 3 months. I was wondering which aerobic exercises would allow me to lose fat and gain muscle that is still feminine. I usually use ellipticals and treadmills, but I notice that my calves get worked a lot. Swimming is not an option. But I'd like to find aerobic/fat-burning exercises (high calorie burning) that allow me to build lean muscle and not become, for lack or a better word, bulgy.
I'm a college student with access to very nice campus gym facilities, so if you know of specific machines or workouts that help, I'd really appreciate your input.