In this paper the results obtained in the last ten years by the authors in the field of sol-gel nanocomposites for optical applications are reviewed. Two type of applications are, in particular, discussed: (a) nanocomposite materials containing semiconductor quantum dots for photonic and optoelectronic applications; (b) nanocomposite materials for optical gas sensing. Nanocomposite multifunctional materials, based on the incorporation of QDs in inorganic or hybrid organic-inorganic matrices, characterized by stable optical properties, good chemical stability, and easy processability, can be obtained using the sol-gel method in combination with colloidal methods. Optical gas sensors based on surface plasmon resonance (SPR) demonstrate great potential both for better understating the chemical interactions at the nanoscale and the development of real devices. A careful control of the film structure allows to achieve very selective gas sensors with tailored microstructure. In both type of applications, the general aspects related to the synthesis and characterization of the materials, and the results obtained in the specific cases, are described with the aim to give an overview of the development of these materials.