Marketing to Marketers Online Resource Center 

There's nothing worse than desperately seeking a quick, authoritative resource for a marketing topic you know nothing about (although your client does not know that and never will), and getting 1,450,273 so-called "relevant" search results back in return. Web Marketing Today (by Dr. Ralph F. Wilson) is an excellent place to get up to speed on most any marketing- or ecommerce-related subject, from affiliate programs to link exchanges to shopping carts to email newsletter publishing.

In addition to Dr. Wilson's own articles, ebooks, product reviews and so on, there is a Web Marketing Info Center organized by topic. It includes hand-picked links to articles from around the Web (10,000 and counting articles, btw). The site offers both no-cost and subscription-level access (which runs $49.95/year), plus a very informative complimentary newsletter.

One of the features of the paid subscription is an email that you receive once a month. It really covers the waterfront of Internet marketing and includes links to articles that have appeared all over the Web over the past 30 days. The articles are broken down into categories, such as automotive, SEO, PPC... you name it. As a matter of fact, Larry Chase (the publisher of Web Digest For Marketers) can personally attest to taking at least two hours out of every month to ferret through all of those articles, just to decide which ones warrant further consumption.