Recently a Nature article by Bramwell et al. show that in a certain kind of magnetically frustrated material called 'spin ice' one can see evidence of 'magnetricity' - a flow of magnetic charges just like electrical charge flow, and understood in terms of a magnetic analogue of the theory of electrolytes. (The material in which this has been observed is dysprosium titanate pyrochlore). The experimentalists actually observe real magnetic currents and are hence able to measure the magnetic charge ('monopole'). This, I believe, is the first example of a system where there is perfect symmetry between electric and magnetic charges. (The popular press has occasionally reported the existence of flux tubes -- dipoles which move independently in certain magnetic materials -- as equivalent to magnetic monopole quasiparticles but the present effect I believe is different -- I would appreciate some comments on these from experts).
One should realise though that this does not change Maxwell's equations in free space. Magnetic monopoles in free space have not been observed yet, except in one un-replicated experiment by Blas Cabrera in 1982. Thus, electromagnetism text books don't need to be revised any time soon.