Femtosecond pump-probe studies provide a sensitive characterization tool for the study of ultrafast relaxation processes in intercalation compounds, more specifically in the alkali metal intercalated fullerenes K3C60 and Rb3C60. Films of these materials were excited with femtosecond optical pulses and the induced transient changes in the optical properties were then monitored with a delayed probe pulse, revealing excited state relaxation dynamics occurring on a picosecond or femtosecond time scale. Room temperature measurements with a 20 fs pulse show extremely long-lived coherent phonon oscillations of the Ag molecular mode at similar to 492 cm(-1). Information about a highly damped vibrational mode involving an alkali metal cation beating against a C-60 anion has also been obtained. Low temperature measurements were also performed, yielding new information about the quasi-particle dynamics in the superconducting state and across the normal to superconducting phase transition. These results are discussed in the context of intercalation compounds based on carbon.