this shows past, present and future hirings for each firm, break down by gender, ethnicity, even sexual orientation. It shows which schools firms OCI at, what they are looking for, what their philosophy is, who the hiring partner is, how big the firm is, break down by partner v. associate, what areas of law they practice in, etc.!!
ALSO, they have a mail merge option in case you wanted to do targetted mailing. mail merge costs money, but most career services at schools have already paid so it is free to you (and if not, it's really cheap anyway).