Knews Multilingual Newsletters allows you to build multilingual professional looking newsletters.
WP Subscriber Form adds a subscription form to the end of your content.
BackWPup allows you to backup your WordPress database, files, and more.
Theme-Check allows you to run checks on the current theme before uploading to WordPress. This plugin uses the same API and is kept more or less in sync with the WordPress.org uploader tool.
WP SlimStat is a simple but powerful web analytics plugin for WordPress.