In the past years, control systems of cars have moved from the analog to the digital domain, and these changes affected the communication subsystems too. The next step in this direction is achieving a higher degree of performance, dependability and integration, so as to meet the needs of tomorrow's more and more demanding applications. In particular, x-by-wire systems are appearing as the challenge that will drive research efforts of the whole automotive industry for the next decade. This means that new technologies have to be developed for in-car networks, in order to provide the high performance required by the next generation of automotive systems. TTCAN, TTP/C, Byteflight, FlexRay and Bluetooth are some of the most promising emerging solutions that have already been defined and can be embedded right in new projects. In the automotive context, it is of paramount importance being able to evaluate the key features of each solution, as well as to verify whether or not they are able to meet the requirements of specific application fields. In this paper these technologies are discussed and their characteristics are compared, pointing out the main advantages and drawbacks.