Anything from seasons 4-9 does it for me. Those episodes were just joke after joke, and the social and pop culture satire was top notch. Granted, there were some classic episodes before then (Homer at the Bat comes to mind), but the show hit its stride in those years. Season by season, some of my favs:
Season 4: Mr. Plow, Marge vs. the Monorail, The Front, Krusty Gets Kancelled
Season 5: Too many to name, but Homer Goes to College, The Boy Who Knew Too Much (MacArnagle!!!) and $pringfield are classics.
Season 6: Itchy & Scratchyland, Homer the Great, A Star is Burns (perhaps my favorite episode), Lisa's Wedding.
Season 7: Who Shot Mr Burns?(part 2), The Simpson's 138th Show Spectacular, Team Homer, Scenes From a Class Struggle in Springfield, 22 Short Films About Springfield, Homerpalooza
Season 8: The Homer They Fall, The Springfield Files, Homer's Enemy, Simpsons Spin-off Showcase
Season 9: The City of New York vs. Homer Simpson, The Last Temptation of Krust, The Trouble With Trillions