Is it possible to split baryons and extract useable energy out of it? Since baryons (e.g. protons, neutrons) are composite particles it should be possible to split them apart. If so, is it then possible to extract useable energy out of the splitting of baryons in analogy to nuclear fission?
 A: In the standard model, baryon number is conserved.  The proton, being the lightest baryon, is then stable.  Anything you change it into has higher mass and will absorb energy.  All other baryons are unstable in isolation and will decay, releasing energy.  Unfortunately, free baryons aside from protons are hard to come by.  Generally they must be produced, and energy conservation demands that takes at least as much energy as you will get out.  
In some models, baryon number is not conserved and you could imagine finding a way to trigger proton decay, which would release energy.  It seems quite unlikely. 
A: I'm not entirely sure about this answer, comments appreciated
If you want to know if breaking a baryon into three quarks will release energy, this will never happen. Charge confinement makes it incredibly hard to separate quarks, and a free quark is pretty much an impossibility — the energy you pump in will turn into extra quarks that bind to the momentarily "freed" quark leaving you with more mesons and no usable energy.
However, if you don't mind splitting it into smaller bits that aren't quarks:
Most baryons decay into mesons and leptons. Since a meson is just two quarks, one can think of it as "a part of a baryon". However, the types of quarks will be different (baryons have all quarks or all antiquarks, mesons have a quark and an antiquark), so I personally do not consider this to be "splitting of the baryon"
However, energy is released in this decay. Theoretically (in some BSM models), protons do decay, but as of now it has meagre experimental backing, and the decay has too large a half life to be useful.
Of course, on can extract energy from a baryon by introducing it to its antibaryon, and this may give a net positive extractable energy in the future though currently creating particles is very energy intensive. Viably creating them in large batches for any such process is impossible
A: Just a point of note: You can "split" neutrons and get useful energy out of them by doing nothing at all. A free neutron has a mean lifetime of around 15 minutes, and will undergo beta decay if you wait long enough. 
A: To split baryons you would have to have free quarks, which as, Manishearth also says, is not possible. The quarks are only asymptotically free, which means in fact at very high energies. One would have  to put a lot more energy in   creating a quark gluon plasma than one could get out of it. 
There also exist the weak interactions, and the neutron decays through them. But neutrons cannot be stored outside nuclei. Their decays contribute to the energies released by fission reactors, so it is baryons disintegrating that contribute to fission energies after all.
Protons are stable enough and in some models their decay is theorized.Experimentally proton  decay has not been observed and the limits set it outside any useful contribution as an energy source. 
