Really Good Emails - A large collection of good product email design.
LibHunt - LibHunt tracks mentions of software libraries on relevant social networks. Based on that data, you can find the most popular projects and their alternatives.
Good Sales Emails - Best sales emails from great companies
AlternativeTo - AlternativeTo lets you find apps and software for Windows, Mac, Linux, iPhone, iPad, Android, Android Tablets, Web Apps, Online, Windows Tablets and more by recommending alternatives to apps you already know.
Great Email Copy - A dose of emails from around the web.
JSter - JSter is a community-driven catalog of the most useful javascript libraries.