This plugin allows you to use custom templates for posts, just like in the pages section.
PHP Code Widget
If you ever need to add PHP code in a widget, use this plugin.
JP's Get RSS Feed
This plugin lets you grap a feed off another site and show it with a shortcode.
Contact Form DB
This plugin collects data from submitted forms for interaction later.
This really helps when you need to clone a lot of posts or pages with minimal modifications only.
This plugin lets you set an expiration date for your posts/pages.