How do you diversify your skill other than in the IT sector?

While I learn a bit about finance, I learned that it emphasize the importance of diversifying your investment portfolio to minimize risk. I suppose it should apply to our professional skill as well, it's better if we can do something else in case the IT sector goes bust. I wonder how do you guys attempt or achieve this diversification. Myself, I have a computer degree, have been working as a software since. I maintain healthy interests in other fields, such as history, languages, and some sciences, but nowhere to a professional level, e.g. I'm nowhere near being a history professor.