Individual mobility is one of the most important needs of modern society and an important link between private, public and economic life. In contrast, transport also entails severe environmental and social burdens, foiling current efforts for sustainable development. As the main source of CO2 emissions, transport is a prominent driver for climate change, and individual car traffic is responsible for nearly a third of the total energy consumption. However, we have to consider that many commuters feel indeed very dependent on their car. Here, ridesharing promises to contribute to environmental protection, while still offering individual mobility. Although ridesharing options have been discussed since many years, internet and smartphones provide completeley new opportunities to find ridesharing partners today. Thus, this book deals with current efforts on implementing flexible internet- and phone-based ridesharing services. With a main focus on the users‘ perspective, their demands and acceptance limits, we aim to explore success factors for non-profit, but also commercial ridesharing concepts.