In The Birds by Aristophanes, we learn a little bit about Gaia's own creation story. If she's the mother of everyone, how was she born?
The Roman poet Ovid collected all kinds of wild stories about the gods in The Metamorphoses. In Book 1, Gaia is pretty much the bomb dot com.
In Anthem by Ayn Rand, one of the characters reclaims her identity by changing her name to Gaea. You go, girl.
Although she doesn't mention her by name, Maya Angelou's "Africa" is definitely about our lady, Mother Earth.
Check her out as a comic strip character in Doctor Strange # 6 (Marvel Comics).
Gaia made a few appearances in this awesome animated series, Captain Planet and the Planeteers.