Self-determination theory

Overview
Self-determination theory suggests that there are three important ingredients for psychological well-being and which foster intrinsic motivation:
 * Autonomy - Having a sense of personal control over life circumstances
 * Competence - Having sufficient skill and knowledge to handle life circumstances
 * Relatedness - Having at least some warm, positive, supportive relationships

Taxonomy
Deci and Ryan (2000)'s taxonomy of motivation describes a motivational spectrum that includes amotivation, four types of extrinsic motivation, and intrinsic motivation.