During the search period, your son needs to be busy writing OSS. Patches, documentation, etc. will all buy him some good 'street cred'.

This is one of the neat win/win things about OSS. He gets credibility, the community gets a few patches and maybe some better documentation. Depending on the work, it could even be part of a portfolio and would certainly be resume-worthy.

I would be *very* interested in a candidate who had spent time productively helping others this way.

Update: I struck 'helping others', because it sounded like working on OSS is purely altruistic, and I don't think that's actually correct. Everybody gets a benefit, even the author, so it's far from selfless. As a matter of fact, I find it completely acceptable to do it for selfish reasons (self-education, self-enrichment, improve employment prospects, search for glory, software *exactly* how you want it, whatever floats your boat.)