To copy from Wikipedia: In the beginning, both Looney Tunes and Merrie Melodies drew their storylines from Warner's vast music library. However, eventually the two series distinguished themselves by Looney Tunes becoming the urabrella for the studio's various recurring characters, while Merrie Melodies continued with the use of one-shot characters. Also, from 1934 to 1943 Merrie Melodies were produced in color and Looney Tunes in black and white; after 1943, however, both series were produced in color; the only real difference between the two series was in the variation between the opening theme music and titles. Both series also made use of the various Warner Bros. cartoon characters
Since I've been watching clips from YouTube and from my DVD, I figured we could get something rolling