BodyThere are quite a few different ways in which a high Body score is a good thing for your Sim. First off, the obvious benefit is that it helps you out in a few careers, but it will also improve your chances to win in a fight, your ability to dive off a diving board, and in general perform well in any interactions that require some degree of physical acumen. Perhaps the most intriguing aspect of Body is that, upon increasing your skill to level three or higher, you'll unlock the Yoga self-interaction.
To begin, though, you'll need to get your Body skill up. There is a cheap exercise machine that you can purchase if you wish to get a good workout, or you can settle for working out via the TV or a stereo if you can't afford the space. Swimming is also an option, if you're willing to head out to a Community Lot and spend a few hours or so in the pool, although this can be a bit time-consuming (in real as well as Sim life), compared to the benefits. After you proceed upwards into the Military and Athletic tracks, you'll unlock the Exerto Exercise Machine, Punching Bag, and the Obstacle Course, all of which are great ways to get a bit of an extra boost to your Body.
As mentioned, though, Yoga should start appearing as a self-interaction when you reach level three in the Body skill. This is something of a hidden sub-skill, in that you can improve your Yoga abilities when you perform the interaction itself (which also increases your Body skill as well). Yoga is more of a cool thing to show off with than it is functional, but as you keep performing it, you'll eventually unlock more interesting animations (such as those shown in the opening cinematic for the Sims).
Logic doesn't have many applications outside of careers, although it can increase your chances of winning a chess match, or when you play the Game Simulator against another Sim. You can increase your Logic via using a telescope (just don't get abducted by aliens while doing so!), via playing chess, or with either the Prints Charming Fingerprint Scanner or the Simsanto Biotech Station, which are unlockable in the Law Enforcement and Science careers, respectively.
If you raise your Logic up to level three, you'll gain the ability to Meditate. Meditating is similar to Yoga, in that it's a quasi-hidden skill with differing abilities based on how long you perform it, but Meditation offers you some extra self-interactions with actual utility. To begin with, your Needs and Mood will freeze while you Meditate, which can be quite useful. If you've built up your Mood enough to ensure positive interactions, you can Meditate while another member of the household calls over whomever you intend to woo or interact with; or you can freeze your Mood before heading off to work if you're edging for a promotion. Later on, you'll gain the ability to levitate while you concentrate, or even to teleport to distant locations on your lot! No mind bullets, unfortunately, but we'll take what we can get.
CreativityIf you want to have a shot at making a bit of extra cash without having to having to deal with the muss and fuss of actually going to work, your Sim can try to earn her keep by using the Creativity skill to create art which can then be sold. If you use a computer to Write A Novel, you'll have to spend a bit of time on it before it's completed (30 hours of Sim time), but you'll gain Creativity all the while. Alternatively, you can try to use an easel to paint; the paintings that result will be salable as well. You won't necessarily make a lot of money doing this, mind, and you almost certainly won't make as much cash as if you were working on advancing along a job track, but these are decent ways to spend your time if your Sim is unemployed or taking care of a child. The amount of money you get for a novel or painting is dependent on your Creativity score; paintings also become more valuable over time, if you keep them around the house. When the painter dies, the paintings get an immediate boost in value.
Besides the aforementioned easel and computer, you can also use a piano to boost your Creativity score, or the Simsanto Biotech Station (Science reward), or the AquaGreen Hydroponic Garden (Slacker reward).