I go on youtube and just look up videos compilations of types of music I like.. I do it while I work during the day.. I usually will find 1 song I like out of like 20 and then i download the mp3 and take it to the gym.
i cant say i have a favorite song, I like to change up my music constantly. generally I am not a rock, heavy metal type person though... I like dance music or 80's, and even epic classical is fun to listen to while I workout. something from ES Posthumus