I've been trying to get a handel on most of the mainstream, and less mainstream theroies out there reguarding gravity, but not sure i've found them all.
1. Quantum Gravity: - Gravity is a function of a force carrier particle called a graviton, which interacts at the speed of light.
2. Einstien/Newtonian Gravity: - Gravity is a curvature of space when mass or energy is present, the curving of space is near instantanious.
3. Gravity as Property: - Gravity is an intrestic property of space/time itself and neither a particle nor a force. Remove all the matter and energy just leaving space itself, and there will still be some intristic gravity. (Ref: Hubbles Constant). Mass and Energy concentrate the effects of gravity locally through spacial compression. Although gavity in this construct is always present (intsantanious) Variations in mass/energy can cause gravitational ripples(waves), which propagate at near light speeds, due to the limited mass/energy which formed them.
4. Gravity Duality: - Gravity is a curvature of space time, and also has a quantum particle/wave components. Therory seems to fit some emperical evidence of the other throeies but has a major flaw in that it can violate conservation of energy through a 'run away' gravity effect. (the run away effect does describe the catastopic univere collapse therory well though)
5. String Theroy Gravity: - I don't understand this one, someone would need to fill in the blanks here.
6. Particle Symetry Gravity: - (Disclaimer: This is my own pet theroy of which I invented to explain the light speed reaction of gravitons, but the seemingly faster then light proagation of the attractive force. I freely admit to not knowing enough high level match to figure out how to put this down and make mathmatical predictions with it.) - Gravity is a composite virtual particle made from joining of therorectical negative 1/3 mass Tacheon (nutrino like) paritcles and therorectical negative 1/3 mass Kronotron (time) particles, and a 2/3 positive mass quark. When these particles team up, a zero mass product is formed (called Gravitons) that always travels at the speed of light (if unbound) but decays quickly. The Oddity here is that the 2/3 mass quark is normaly already bound in a normal particle. Rhe attactive force of gravity a result of the decayed Tacheon/Kronoton pair (traveling at faster then light sppeds) recombining with another 2/3 mass quark in another normal particle. The exchangeing of Tacheon/Kronoton pairs between normal mass matter causes the attration between the two due to temporal effects of faster then light exchange causing a momentary link. The Tacheon/Kronoton pair arrives at desitnation just slightly before they left causing the two normal mass particles to be temporaly linked and be attracted to each other during the duration of the temporal discrepancy.
7. Pushing Gravity - Gravity is a repulsive force pushing object together. (After thinking on this one is appears to have exactly the same problems regular gravity theroies has. It's Akin to the thought experiment is our universe Matter or Anti-Matter? Is Gravity Attractive? or Repulsive? A fun experiment but the end result seems to be being unable to tell the difference. Probably should be called Anti-Gravity Therory)
8. Looping Quantum Gravity - Ok this one threw me for a loop literaly and don't even understand the basics of it yet. Another one to be filled in.
9. Graviton/Dilaton Gravity - Found this mentioned on the AIP (american Institute of Physics) site. Where Gravity is a combination of a 2 spin particle (Gravitons) and a 0 spin particle (Dilaton).