First Stop: NW Career Services
NW's Career Services has LOTS of internship resources for you! Start here!

American Advertising Federation/Kansas City and Omaha Chapters:
AAF-KC (KC Ad Club) Jobs Board
AAF Omaha Jobs Board

Web Resources for Internships
CollegeGrad [and see this newly added feature]
Rising Star Internships
Prof KRG Media Internships
Job search sites that focus on advertising jobs:
Google Jobs
Yahoo Careers
Yahoo Internships.html 

Internships with non-profits:

Other sources to check out:
Marketing and web jobs blog: Kansas City Job Seekers

Jobs in the Magazine industry
For freelance networking in Kansas City:  KC Freelance Exchange

Kansas City Networking Opportunities:
If you want to get into the KC advertising scene, there are a few places to look into. The first, and most important, is the Kansas City Ad Club. Here's a direct link to a calendar that lists some very important parties and volunteering opportunities -- this is where it all happens, guys!!

You also should check out this group: The Art and Copy Club. Their web site has a lot of resources, and if you spend some time with it, you'll find some networking opportunities, too.

Other KC clubs:
Ad2: for KC's younger advertising crowd
KC Business Marketing Association
MediaMix: for KC's media buyers and sellers