Hoover would have made major changes to the Stock Market. He would have ended insider trading and any way of artifically raising stock prices. This would have helped stave off the Depression for a few years.
On the foreign scene he would have urged a national moratorium on war debts, thus styfling the rise of Adolph Hitler in Germany. He also supprted the League of Nations, so this could have led to a fight with the conservative Senate under Henry Lodge. His humkanitarian side could have led to an early Marshall Plan for war ravaged Europe helping end the rise of Communist and Fascist governments.
On the deomcestic scene he would have regulated parts and radio frequencies, supported Civil Rights legislation, and handled the flood of 1927 as well as he did in real life.
Though Hoover was certainly not as bad as he often gets the reputation of being, he was not the saint you describe. He would have been internationalist but continued a hard line toward Germany and would have been less willing to work with the Soviet Union, contributing to earlier tension in Eastern Europe. While Hoover's economic reforms long before the Depression prevented the disaster Coolidge engineered, the Depression still occurs, though more severely in Europe and less so in the United States.
Extrapolating:
Instead of Nazis, Germany is eventually taken over by Communists promising an end to Germany's economic troubles. World War II is postponed, but instead a sort of "Cold War" exists by 1940 between the League of Nations, which has become more of a military alliance among Democratic powers than a political entity, and the Comintern. However, without WWII, there are no nukes and thus no mutually assured destruction, meaning that war would begin at some point, possibly as an extension of the Chinese Civil War. (The United States, maintaining a robust economy and bereft of its European markets that are in the midst of a depression, seeks markets in China and becomes more personally involved in support of the Nationalists.)
