Both JupiterResearch and Forrester launched a report on email marketing recently:

Forrester: Relationships Write The Next Chapter For Email
Email success among marketers of apparel, home goods, or travel is obvious because it's measured in sales. Financial services and consumer packaged goods (CPG) manufacturers find the value of email more challenging to defend because they are limited by security and data constraints, or because they don't sell direct to the consumer. However, precisely because of these constraints, email practitioners in these industries have developed some great relationship-building best practices that any interactive marketer can leverage. All practitioners should infuse their emails with user-generated content and increase their usage of analytics to deliver ever-more relevant messages.

JupiterResearch: E-mail Marketing Adoption - Assessing Multinational E-mail Marketing Sophistication
US e-mail marketers will face increasing competition from their European peers as they begin to explore international e-mail opportunities. US e-mail marketing vendors seeking European expansion are therefore questioning the many unseen hurdles that lie ahead. Key questions that are answered in this report are:

• How does the sophistication of e-mail marketing differ in the US and in Europe?
• Which regions are relatively less likely to adopt relevance as a tactic, thus stifling mailing performance?
• Which vendor categories and features are likely to flourish in various regions?