TiO2 nanomaterials, in general, have over the last 30 years attracted tremendous scientific and technological interest, due to a wide range of functional properties of TiO2 which make it promising for instance for photocatalysis, use in Grätzel type solar cells, electrochemical devices, or in biomedical applications. For many functional applications, 1D and highly defined TiO2 nanomorphologies can be superior to nanoparticles. A highly elegant route to grow TiO2 nanotube arrays is by self-organizing anodic oxidation. This approach is not limited to TiO2, as a full range of other functional oxide structures on various metals and alloys can be formed, and the chemical composition and morphology of the structures can be varied in a large range. As the structures can be grown on conductive substrates as ordered layers, they can be directly used as functional electrodes (e.g. photo-anodes). The presentation will focus on these highly ordered nanotube arrays of TiO2 and discuss most recent progress in synthesis, modification and applications.