Over 125 years ago, the Populist Movement launched a third party in the US and their most compelling platform plank was "greenbacks," the elimination of the rigid gold standard and a freeing up of the money supply. Here we are over a century later and Richard Nixon freed us from the last vestiges of Gold in forty years ago and our central Banksters have expanded the money supply at the behest of Presidents and their Bankster allies. Deflation and tight (exploitive) credit were the problem in the 1880s and after the "money problem" was solved with greenbacks, the Masters of the Universe have figured out how to game that system for the same outcome: squeeze the 99% and extract as much for the 0.1% as possible.
Ellen Brown has been writing about the "money problem" for some time. Her *Web of Debt* is a comprehensive look at the problems with the current "money as debt" system with the debt owned by commercial bankers. She is a proponent of a state-produced money with no associated debt and of state-owned banks. She popped up today with an essay, "Are Cooperative Banks the Wave of the Future?" which puts cooperative financial institutions into the context of the rest of her thinking.
Ellen has not (yet) bought in to the Solidarity Economy or the Cooperative Movement, per se. She recognizes the value of socialized finance, finance where private profit is subordinated to other goals, primarily service to the community. It is valuable, however, to recognize her contribution to legitimizing this part of the Solidarity concept.