Power Rangers in Supernatural
Emma Lahana (Kira in Power Rangers Dino Thunder)
as Jen in Supernatural 2x15 - "Tall Tales"
Alycia Purrott (Syd in Power Rangers SPD)
as an unnamed film star in Supernatural 2x18 - "Hollywood Babylon"
Erin Cahill (Jen in Power Rangers Time Force)
as Elizabeth in Supernatural 3x09 - "Malleus Maleficarum"
Jorgito Vargas Jr. (Blake from Power Rangers Ninja Storm)
as an unnamed janitor/jerk in Supernatural 6x14 - "Mannequin 3: Reckoning"
And although she wasn't technically a ranger...
Sandra McCoy (Kendall from Power Rangers Wild Force)
as a Crossroads Demon in 3x05 - "Bedtime Stories"
(Bonus Trivia: Sandra dated and was at one point engaged to Jared Padalecki, one of the main stars of Supernatural.)