Aside from being that character in the book, she is played in the upcoming movie by Elizabeth Banks.
However, you should probably only pay attention to THIS DESCRIPTION...
Effie Trinket is a flashy, colorful, mildy entertaining freak-o in the book who is overly eccentric and scares people while haunting their dreams...
She may or may not want your soul.
Bob: "Dude, Effie Trinket haunts my dreams."
Bob's Mom: "Go drink some more cough medicine, sweetheart."
Katniss: "Don't worry Prim, it's your first year, you're not gonna get picked."
Effie Trinket: "Challenge accepted. Primrose Everdeen!"
Katniss: "You b@#$!! Crap I guess I will volunteer as tribute."
Peeta: "Anyone want some bread?"
Effie Trinket: "Fine, Peeta too."