Mechanical devices in combination with modern semiconductor electronics offer great advantages as for example their robustness against electrical shocks and ionization due to radiation. The main disadvantage of mechanical devices so far is the low speed of operation. This has been overcome with the realization of nanomechanical systems (NEMS), which allow operation at frequencies up to 500 MHz. I will discuss recent work on such nanomechanical resonators focussing on nonlinear dynamics, mechanical mixing, parametric resonance, and possible uses in quantum squeezing experiments. Furthermore, I will present record mechanical quality factors of Q > 10000. Finally, I will outline an approach to using NEMS for applications in biology (Bio-NEMS).