As most peoople who is nowadays interested in quantum theories of gravity knows, there is in the internet something called "string wars". These "wars" consist on a dialectic batlle betwen some string theorists, with Lubos Motl as the main contendient vs some people who claim that string theory is dead (mainly Peter Woit) because of it´s lack of experimentally falsifiable predictions and other people (mainly Lee Smollin) who defends that even if string theory is a legitimate theory there are another aproachs to the problem of the quantization which deserve more funds, mainly LQG.
In these blog I have had entries about strings, LQG, NCG and (the last one) conformal gravity, which in greater or lesser extent claim to have something to say about quantum gravity and links to some pages about these topics. Also I have linked the Mitta Pitkannen blog (http://matpitka.blogspot.com/) which is devoted to "topological geometro dynamics" about which I havent made any entry simply because I don´t know enought of it to do so, but which is (or at last I tnink it is) another proponent as quantum gravity.
These doesn´t exaust the list of "roads" (an Smollin terminology) to quantum gravity. For example a very famous and well considered physics, Roger Penrose, thinks that maybe when he would be able to develop it enought its twistor theory could be a candidate as a quantum gravity (nowadays it is mainly a math tool apropiate for some tasks, but very awfull for many others). If someone is interested the other famous English physician, Stepehn Hawkings, defends his own aproach,euclidean quantum gravity. I have knowledge about a few others but I am not interested here in making an exaustive list.
One could answer, and it is a very reasonable question, why to bother with so many theories? Afther all string theorists insist in that althoguth they have not experimental avals they have made many self-consitency tests and they are sures that string theory is the only "game in town". Well, of course these sounds like a "no-go theorem" and as any other no-go theorem it is as solid as the weakest of its asumptions. I am not going to go into the details now but the main point in these claim is that string theory represents an scenary where quantum theorie, just as it is nowadays known, is preserved. On the contrary LQG people would defend the gravity expert viewpoint.
Other theories, like NCG (non conmutative geometry) could have a place as "effective theories" in some range (these is the way string theoriests seem to think about it) or as a separate theory (the Alain Connes viewpoint).
I have not intention in these blog to get any position in these wars and neither to give any support to personal attacks in the line of "crankpots" pursuit (at least not for academically acredited people, "Subiiris" or "Paulinos" will have zero tolerance) . Thse doesn´t mean that I don´t have my own opinions, nor that I consider equally likelly all these aproachs, and of course I will not dedicate the same time to learn all of them. But I think it could be interesting to present, at least in overview from tiem to time, some of the less known theories. I guess that an inteligent and prepared enought reader can make his own idea of how viables these theories are.