Adresources.internet.com  Includes statistics, sample ad rates, top advertisers and news for web advertising.

Advertising World: The Ultimate Communications Directory (from the University of Texas). Extensive collection of advertising links on the internet.

Interactive Advertising Bureau. Some free, brief reports on web advertising, under Resources and Research tab.

Web Marketing Today Information Center.  Links to hundreds of articles about marketing a business on the web.

 

Also check out the library catalog for books on web advertising.