If you recognize her at all, it's as Ellen Page's bestie in Juno. Olivia Thirlby is one of my favorite actresses. She has not had a great run of late, but when she's in a good part, she's dynamite.
For a moment after The Wackness, it seemed like Thirlby was on the cusp: she was included in Vanity Fair's 'new wave' of young actors in 2008, and had a taste of bigger budget genre fare with The Darkest Hour and Dredd. However, those movies bombed (Dredd at least had the benefit of good reviews), and ever since Thirlby has largely stuck to supporting roles, mostly in experimental and indie dramas.
Dredd is probably the most interesting role from this period, and while the box office snub may have killed her momentum a bit, that should not take away from her performance in the film. In a movie built on minimalism and economy, Thirlby's understated performance is a perfect complement to the movie's pared down aesthetic. Since the character arc of movie ultimately rests on her shoulders, it is a tribute to her abilities that she manages to transcend her slight build and make Anderson a believable action heroine.
Thirlby has several films either in post or due for release. Hopefully, one of these roles will give her the heat she needs to get the recognition her talents deserve.