TestSubject - Test how your email subject line displays on mobile devices.
Gmail Mail Merge - Send personalized emails with attachments
Canned Emails - A minimal site with prewritten emails
Dynamic Campaigns by Sigstr - Share the most relevant content in every email
analyze.email - Test the spam-y-ness of your emails
Dynamically Personalized Emails by QGraph - Hyper-personalized emails for E-commerce