With present-day technology, spins in semiconductor quantum dots can be created, coherently manipulated, and measured. The ability of controlling spins in semiconductor nanostructures has new and exciting applications in electronics and information processing, including quantum computing and quantum communication. We give an overview over some of the theoretical work motivated by the potential use of electron spins in quantum dots as qubits for quantum information processing. Quantum gate mechanisms in laterally and vertically tunnel-coupled quantum dots acid methods for single-spin manipulation and measurements are presented. Entanglement acts as a fundamental resource for many known quantum information processing schemes. We discuss recently proposed schemes to detect the entanglement of electrons in normal and superconducting wires via transport and noise measurements. (C) 2001 Elsevier Science B.V. All rights reserved.