Some unusual electronic properties of doped manganites are described. The low temperature resistivity of the metallic ferromagnet has a large $T^2$ term. The residual resistivity can be much larger than the Mott maximum, and depends exponentially on spontaneous magnetization. There is much evidence for strong spatial and temporal fluctuation effects. The available theories are discussed in the light of these phenomena, and it is suggested that a novel localizing mechanism is at work, leading to extreme sensitivity of physical properties to small atomic changes.