You need insider contacts *play james bond theme here*
Students I think are very fickle when it comes to services like this. What you want to aim for is word of mouth marketing, so that students will tell their friends about it.
Find at least 1 popular person in every college and have them do various regular marketing activities in their college in return for some kind of incentive (probably cash).
Send them flyers, *free* t-shirts (
hint, no one will buy a $20 t-shirt with just your logo and link on it) and various other merchandise to handout to people. You could hold competitions like "design a collegemedium t-shirt" or "tell people about collegemedium and get X" or partner with another company that sells/offers something of interest to students (alcohol perhaps) and do joint marketing and competitions with them.
But customise each marketing campaign to individual colleges. e.g. students from say Stanford would rather wear a good t-shirt that says "Stanford CollegeMedium" rather than just "CollegeMedium". And perhaps re-work your URLs to indicate that:
www.collegemedium/stanford or stanford.collegemedium.com
Aim to have soo many collegemedium messages in a student's life that they will instantly recognise when they want to sell or buy something they go to your site. So they need to be exposed to your brand at least 7 times. If you can have students see your brand 7 times per day in every college in the US... then you should be good.
And finally... survey the students to see what marketing would work best. I'm just one, Australian student, so obviously these are just ideas I think would be good for my particular demographics.
cheers
nathan
