Marx, for example, thought that use value was a prerequisite for labour-produced stuff to become commodities, as mud pies are not valued prior to being offered by their producer for exchange. Even Menger employed the term use value in his formulation of radical subjectivism.
The use value that Marx talked about was objective. As for Menger? Well, it's actually debatable.
But anyway, onto the porn.
Economics Concepts offer a utils-heavy explication of marginal utility theory.  The Khan Academy has fantastic videos. The one linked is great at explicating total and marginal utility and substitution. But, yet again, it uses utils. Utility does not have units! Economics does not have units! That's precisely why econ is not a hard science.  Several others give short explanations summarising key points. 
WikiHow offers the one I like best. It manages to avoid utils until the third of its three parts. For its first and second parts it simply uses money prices.  We finish off with The Incidental Economist and Learnerator. 
Give them all a go!
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