For the development of microsystems, actuators are required which can be triggered in various different ways, can be scaled down to the micro-range, and allow a cost-effective manufacturing process. Of special interest are materials which transform electrical into mechanical energy as they can directly be used as actuators. The corresponding energy conversion mechanisms are magnetostriction, piezoeffect, and shape memory effect. Especially thin film deposition of these materials present interesting opportunities to realize micro-actuators or sensors as they offer features like simple actuator design and mass-production compatible to microsystem manufacturing processes. This paper contains a description and discussion of various transducer materials like magnetostrictive films (amorphous, nanocrystalline and multilayered rare earth-Fe alloys), piezoelectric films (wurtzite- and perovskite-type materials), and shape memory films (TiNi-based alloys) which--as compounds with suitable micromachined substrates--can be used as bending transducers. Based on these materials' development, typical applications of these smart film compounds as actuators in MEMS (e.g. microfluidic devices, ultrasonic micromotors, and switches) are discussed.