When we think about sexual activity, there are a few body parts that are generally understood to be key players. These are typically the body parts that will bump a movie's rating from PG-13 up to R. These are also body parts that are typically (somewhat) covered by clothing. The fact that these areas are considered inappropriate for children under 17 gives them a special status not enjoyed by the other 97 percent of our bodies. I mean, can you imagine television stations censoring out hands? Elbows? Ears? But just because Hollywood has decided that these body parts aren't "special" doesn't mean we have to forsake them, too.
As a neuroscience major, I can say with some confidence that the brain is capable of interpreting sensory input from more than simply the mouth and genitals. In fact, a much larger portion of the brain is devoted to interpreting sensory input from the hands or lips than from the genitals. This realization doesn't mean that the genital region isn't important, but it leaves an opportunity to get creative. Realistically, any body part can be turned into an erogenous zone, but for the sake of space we'll focus on a few.
Fingers: These overwhelmingly useful digits are incredibly sensitive, a fact that can be exploited in situations other than testing whether or not the burner is hot. Try sucking on your partner's fingers, one at a time, and coupling that with genital touching. You can experiment with timing and synchronize what you're doing with your fingers with what you're doing to their fingers. Try grabbing your partner's hand and moving it over areas of your own body. This way you can both experience light, sensual touching in a way you might not have before. Incorporate a hand massage, which can feel especially nice after taking a long essay test.
Ears: Ears are a very sensitive part of the body that are generally introduced to the sexual arena with the concept of whispering "sweet nothings." This is probably because people don't generally care for that not-so-sweet something (saliva) pooling in some of their most sensitive sensory organs. There are ways around this, however. Try sucking and nibbling on the earlobe, and then licking behind the ear. You can also trace the edge of the ear with your tongue. Some people like having a tongue stuck in their ear, some definitely don't. It's probably best to ask, or at least go slow, to give people a chance to make their preference known. Breathing softly into the ear can be sexy, especially when you've just moistened the ear with your tongue, but yelling, loud moaning, and panting are not so hot. No one wants to explain to their doctor that they're going deaf because their boyfriend keeps hyperventilating into their ear.
Elbows and knees: I know it may sound gross, but the skin in the folds of your elbows and knees is really sensitive. It can be a nice place to lick or kiss. Also, kissing the inside of the elbows leaves you in a nice position to lick up the arm and to the collarbone, which is a sensitive area. The knees give you a nice trajectory to the inner thighs, which deserve some attention before you wind up a little further north. The inner thighs are very sensitive, and nibbling and kissing there can be a great way to increase your partner's anticipation before you get to the groin.
Feet: Feet are tricky because people seem to either love them or hate them. However, don't discount how nice it can feel to have a foot rub, especially during some licking/kissing of the inner thighs and genitals. Some people also like the idea of having their toes sucked on, so that might be something to ask about if you know your partner's feet are clean. Be wary of ticklishness, though. Nothing ruins the mood faster than a swift kick in the face.
Abdomen and bellybutton: Kissing and licking a path between the belly button and the nipples can be a good way to explore these very sensitive zones while also including the abs. Go a little lower, too, and explore the creases between the hips and the groin. This can be another great way to build anticipation for oral sex.
When it comes to sensual touching, the body is, literally, your canvas. Almost anything can be made erotic when you're in the mood. Exploring under-appreciated areas of the body can be fun and invigorating. Just bear in mind: Moaning is a good sign, as are sighing and the exclamations "yes" or "oh my God !" Demonic, uncontrollable laughter or wild thrashing on the other hand? Probably best to stop before your partner punches you or pees in your bed.