Politico, Real Clear Politics and Reuters all offer up-to-date polling information on a variety of political topics. These resources track polls regarding both the current president's approval rating and the 2016 presidential race, as of 2015.
Both Politico and Real Clear Politics conglomerate raw data from polls from several other sources such as Public Policy Polling, Quinnipiac University, Fox News, CNN, CBS, NBC, The Texas Tribune, and several local and state news sources. Reuters offers information on the polling results, as well as editorial articles regarding the current polls. All of these websites offer polling data for both the Republican and Democratic presidential primaries.