Radio and Internet Advertising websites.?

Hello,
I have a school assignment that requires me to find a advertisement place and their types and cost.

I have chosen to look for Radio and Internet (I have to do 2) but I cannot find any site that tells me what their cost is, they ask for you to contact them, but I really don't have the time for that and I don't want them to think that I could be a customer.

So my question is, do you know where I could find that info?
Thank you for any help.
Kyle

You can find ad rate for many individual sites at BuySellAds.com

If you could switch to local TV, this site would be a good source:

www.cheap-tv-spots.com/