Epoxide derivatives constitute a broad family of monomers which are able to be polymerized by anionic or related nucleophilic ring-opening mechanism. The main synthetic strategies developed are reviewed in terms of polymerization rates, side reactions, and possibilities for controlling such polymerizations. Ring-opening polymerization of ethylene oxide and substituted epoxides utilizing alkali metal derivatives or other initiating systems in conjunction or not with activating systems are discussed. Emphasis is also given on the use of organic initiators or catalysts to trigger the metal-free ring-opening polymerization of epoxides. Functionalization of polyethers is also described, which includes the use of functional initiators, post-chemical modification of reactive functions carried by the polyether backbone, or functional-monomer insertion. A focus is particularly given on the preparation of polyethers bearing hydroxy, amine, allyl, azide and other reactive groups, at the chain ends or in the chains.