Really Good Emails - A large collection of good product email design.
TiddlyMap - An interactive concept- and mind-mapping plugin for the personal note-taking software TiddlyWiki based on the Vis.js library. It's free and open-source!
Good Sales Emails - Best sales emails from great companies
Wisdomap - Wisdomap Medicine is a study aid that helps medical students create differential diagnoses and suitable management plans from a presenting complaint and structured revision notes.
Great Email Copy - A dose of emails from around the web.
IOctopus - IOctopus is an online mind map service for a dive deep into the mind for the best ideas.