Episode--Pokemon Emergency!
Chansey is helping Nurse Joy in the Pokemon Center.

Episode--Showdown at Dark City
Chansey comes out of Nurse Joy's pokeball near the end of the episode.

Episode--A Chansey Operation
Chansey practically stars in this episode.  She's helping to nurse all of the injured Pokemon to full strength.

Episode--The Joy of Pokemon
Chansey travels with Nurse Joy around the Orange Islands without Pokemon Centers.

Episode--Ignorance is Blissey(Johto Journeys)
Chansey appears in Jessie's flashbacks of nursing school.

Episode--Hour of the Houndour (Johto Journeys)
Nurse Joy buys ice cream for Chansey and they buy groceries.

Movie Short Film--Pikachu's Vacation
Chansey starts dancing in a short clip.  I think I also saw her in a hot air balloon during Squirtle's and Marrill's race.

Movie Short Film--Pikachu's Adventure
Chansey appears in some trees, I think, and she catches Togepi at the end of the film.