My wife and I are programmers (I was her senior at a company when we met). She gets a free coach/interview practice partner. I get more visibility into companies other than mine (e.g. in terms of compensation, work-life balance, joel test, etc)
Sometimes we use programming analogies to convey ideas to each other that are not related to programming. Work-related frustrations are usually very easy to relate to, since they're often things the other has also experienced first-hand.
I know of a couple whose husband was CTO and that helped the wife get promoted in the company (objectively speaking, she was no slouch by any means). Bit of an outlier scenario, but alas, it plays back to the coaching thing.