Conjugated (or conducting) polymers (CPs) are a group of materials that attracts a lot of attention due to their properties and intrinsic characteristics. They show thermal and chemical stability, low toxicity, and good environment sustainability. Moreover, depending on the doping degree, CPs have an intrinsic electrical conductivity ranging from 10^-10-10^-5 S/cm to 1-10⁴ S/cm but are lighter than metals. When a suitable secondary phase is introduced in a conjugated polymer matrix, mechanical stability, electronic and ion transport properties, as well as electrochemical and electrochromic behaviour are improved. In this way, nanocomposites based on CPs show wide applications in many technological fields. Among CPs, Polyaniline (PANI) is one of the most studied because it is cheap, easily available, and its doping/de-doping degree can be simply tuned, since it depends on oxidation and protonation status. It can be synthesized by chemical or electrochemical methods and does not require stabilizers or solubilizers. Thanks to outstanding properties, its applications are mainly in sensors and biosensors, in electronic and electrochromic devices, in energy storage and production. In this paper, after a short review of the most recent literature on applications of CPs, some interesting original results are reported. In particular, performance of PANI and carbon nanotube (CNT)-reinforced PANI is described in view of their application as supercapacitor electrodes, thermoelectric generator materials, and anti-corrosion coatings.