In a blink-and-you'll-miss-her moment, a glimpse of Hawkgirl can be seen in the preview of the upcoming Young Justice cartoon series.
The series stars several Teen Titans-ish characters, such as Superboy, Kid Flash, Miss Martian, and so forth, but also features the Justice League. In this preview, we see some character designs for the Leaguers, including, in very quick pan, Hawkgirl. Looks like they used the models from Justice League: Crisis on Two Earths.
Since she doesn't have a young counterpart, I imagine Hawkgirl will be a background character. No sign of Hawkman yet.
Young Justice is set to debut sometime in the Fall.