Depending on the FTP daemon that you're running, common wu.ftpd, or proftpd, a good place to start would be www.securityfocus.com. They also ahev mailing lists, and things you can sign up to get the latest in script kiddie needs. :-/ They seem to believe in "full disclosure".
Anyway.. another tip, on the Vuln-Dev mailing list there a new wu.ftpd vulnerability that was just posted either yesterday or today, Idon't remember.