1. Kamp Krusty - Lisa and Bart spend the summer at Kamp Krusty, with hilarious results.
http://en.wikipedia.org/wiki/Kamp_Krusty
2. Homer at the Bat - Mr. Burns brings in ringers to help him win an annual softball game.
http://en.wikipedia.org/wiki/Homer_at_the_Bat
3. The Homer They Fall - Homer learns that he has an extra layer of water around brain which allows him to take unusual amounts of punishment to the head. He becomes a boxer, managed by Moe, and works his way towards a title shot.
http://en.wikipedia.org/wiki/The_Homer_They_Fall