Alicia Silverstone (Jarecki)

Hey, another Alicia!
A modern "flower child" type, Alicia first made a splash as a psychotic ingenue in films The Crush and The BabySitter and as a ditsy ingenue in the film Clueless.
Very involved in ecological and political causes, Alicia recently did a (tastefully) nude ad for PETA (which I've linked below).

Genre appearances include...
Vamps (Goody)
Tropic Thunder (Herself)
Silence Becomes You (Violet)
Alex Rider: Operation StormBreaker (Jack Starbright)
Scooby Doo 2: Monsters Unleashed / Scooby Doo 2: Monsters Unleashed [VG] (Heather)
Scorched (Sheila Rilo)
Rock My Worldaka Global Heresy (Natalie Bevin)
True Crime (Mary Giordano)
Hideaway (Regina)
Blast from the Past (Eve)
Batman and Robin (Batgirl / Barbara Wilson)

Check out...
The Kind Life
(Alicia's personal site about the vegan lifestyle)
Alicia at PETA
Alicia / Batgirl Tribute Page

Other actresses to play Batgirl include...
No one else has played Batgirl / Barbara Wilson (niece of Bruce Wayne's butler, Alfred Pennyworth).
All the other Batgirls have been Barbara Gordon (daughter / niece of Commissioner James Gordon)
(You thought I was gonna list over a dozen other Batgirls?)