Summer started just a few days ago, but we’re not noticing any of it here in The Netherlands sadly: even so, the things that are hot in email marketing in the past few days are below 
Email designs / webmail clients / browsers
Retailemailblog: Another reason to monitor your emails in a variety of inboxes
Campaign Monitor: Guide to CSS – updated June 2011
MediaPost Email Insider: Critical trends in email design
Deliverability / (anti) spam / security / law
Return Path: The Newest Return Path Study Explains Why I Keep Talking about Reputation
MarketingSherpa: Why renting third-party lists is among the worst tactics
Other email marketing news and posts
Inbox Group: Email Marketing for Internal Communications
ClickZ: Testing: why failure must be an option
Social media vs email vs …
Social Marketing Forum: The marketing power of online communities
Marketing Pilgrim: Why email marketing is better than social media