When Dave talks about salvaging parts from his dumpster-diving find, he always says "I'd definitely save the DC/DC converters." An I always have as well... They're also widely available on the surplus market for shockingly low prices.
But ... what do you DO with them? Usually they're "telco system" supplies, with a nominal 48V input. Which is generally NOT a very convenient voltage for hobbyist projects, or even prototyping anything (other than telco gear, I guess.) Also, *minimum* output current tends to be pretty high.