Well I stopped by this section of the forum just to explore and whammo! a great post on ear training by using famous songs. Terrific. Thank you pghboemike! I knew some of these but not all.
In college, we did tons of ear training and intervals were always a challenge. It helps a lot to build a references, like the ones in the videos shared by pghboemike. I like to use the Interval Tutor in Band-in-a-Box to keep my ear in tune. It's such a great skill to have, especially for transcribing melodies and songwriting!