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 Email Copy - Email copy 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.
Good Sales Emails - Best sales emails from great companies
JSter - JSter is a community-driven catalog of the most useful javascript libraries.