  We demonstrate a new method for determining the Fermi velocity in
quasi-two-dimensional (Q2D) organic conductors. Application of a magnetic field
parallel to the conducting layers results in periodic open orbit quasiparticle
trajectories along the Q2D Fermi surface. Averaging of this motion over the
Fermi surface leads to a resonance in the interlayer microwave conductivity.
The resonance frequency is simply related to the extremal value of the Fermi
velocity perpendicular to the applied field. Thus, angle dependent microwave
studies enable a complete mapping of the Fermi velocity. We illustrate the
applicability of this method for the highly-2D organic conductor
k-(BEDT-TTF)2I3.
