Simon Johnson had a nice blogpost in the NYT arguing that populism has often been a source of good economic ideas in U.S. history with a focus on populist sentiment for breaking up too big to fail banks. At one point Johnson notes some of the constructive measures pushed by populists, noting that the direct election of senators and the income tax were both populist ideas.
One other item that should be on this list is ending the gold standard. This was a rallying cry for the populists throughout their history. It was also good policy, as going off the gold standard laid the basis for the recovery from the Great Depression.