Energetic protons (0.39--440 MeV), alpha particles (0.59--52 MeV/nucleon), and medium nuclei (carbon, nitrogen, and oxygen; 0.7--8.8 MeV/nucleon) have been observed with the Charged Particle Measurement Experiment (CPME) aboard the Interplanetary Monitoring Platform 8 (IMP 8) spacecraft from 1973 to the present. We summarize the results obtained for the period October 1973 through November 2000, more than two complete solar cycles. We believe that these observations of solar and interplanetary particles are the longest set from a single instrument yet obtained. Artifacts have been carefully removed from this data set, including background changes due to the failure in 1989 of an electronic anticoincidence shield. We have computed averages over individual solar cycles as well as grand averages of everything seen over the 27-year period. The grand average energy spectrum of protons, alphas, and medium nuclei is well described by a power law function in total energy with exponent -2, where E is in units of MeV total energy and flux is particles/(cm2 s sr MeV). Compositional abundance ratios for energetic nuclei at the same speeds are calculated for times of minimum (H/He = 30; He/medium = 95) and maximum (H/He = 61; He/medium = 45) solar activity. We also considered possible relationships between sunspot number and interplanetary particle flux using a variety of averaging intervals and time lags and leads but found no result that could be used to predict particle fluxes from sunspot numbers over short intervals (typically several solar rotations).