General Online/Digital Marketing

Webmaster World
Discussions on marketing techniques, tips and latest developments inc. SEO, PPC, email, affiliate marketing

Clickz
Articles and opinions on web/ digital marketing issues

Spamcheck
A free tool to check the spam rating of your email newsletter before you broadcast it.

Marketing Sherpa
Latest email news and case studies.

Chartered Institute of Marketing
Marketing resources and networking opportunities

Chinwag
Digital discussion and resource

Affiliates 4 U
Top notch affiliate marketing forum