
Send a query via e-mail, with a brief description in the body of the text.
Try to be as engaging about the material as possible from the outset, though, without being "cute"; in other words "bells and whistles" of any kind are significantly less persuasive than the pull of a good, honest description.
Links:
[1] http://www.lmqlit.com
[2] mailto:rob@lmqlit.com
[3] http://www.pw.org/literary_agents