NWjobs.blogspot.com is a jobs board I maintain just for advertising, IDM and related majors. I post all the tips I get from my contacts and graduates. Sometimes jobs are posted here before they make it to other job sites.
If you’re looking for an on-campus internships, be sure to check the Campus Internships page. There are lots of opportunities for advertising and IDM students right on campus, so check ’em out!