What are the best clock sources for a distribution-only design?

There are numerous potential sources that could be used to drive a distribution only design: a closed loop PLL employing a VCO or a VCXO, a stand alone oscillator or source, a recovered signal from a CDR, etc. The best clock source will vary based on the application needs. For lowest jitter, VCXO's operating in a closed loop tend to have the best performance.