there are too many. off the top of my head:
monorail song
stonecutters song
dental plan
anything duffman
krustyland
frank grimes
the flanders foster bart and lisa
homer on weight disability
$20 can buy many peanuts
jagged metal krusty-o
no, money down! (lionel hutz)
there's the truth....and THE TRUTH!
homer sells his soul for a donut
i've got an army of high priced lawyers
alice's adventures through the windshield
canyonero
homer goes to clown college
my brother made a VHS tape (way back in the day) of all the greatest simpsons episodes ever (circa 2000)