This link takes you to a list of recommended websites for media planning research. Many come from trade associations. Some give access to reports and data for free, some require you to register, some will want to charge for complete access but may provide some data for free. "The following websites can be used to compare media channels (e.g., television versus magazine versus Internet) and to choose specific media vehicles, such as specific magazine titles, cable channels, local radio stations, or websites."
Marketer's Guide to Media - Ask at Reference for current volume (Publication CEASED in 2012)
SRDS - Standard Rate and Data Service
NEW! Fall 2022:
The Winmo database provides data on advertising agencies, advertisers, key contacts, ad spends, media types, and more:
These sources provide generalized costs and figures that may help you estimate costs.
Advertising Age - Data Center Online