Event Calendar / Scheduler
The plugin allows you to manage single or multiple user events through easy and intuitive dynamic interface. Users can add/modify/delete events on the fly and easily change events dates and time by simply dragging the event boxes. You can set up different levels of permissions to people who will use the calendar.
This plugin will allow you to specify certain pages to not be linked when wp_list_pages() is used in your theme. You might want to do this if you want a header for a series of subpages, but don’t specifically want that header to be a real “page” or link.
The Twitoaster WordPress Plugin automatically retrieves Twitter replies to your Blog’s posts. These “Twitter comments” are displayed like comments, on the posts pages they are related to.
The BigTweet button allows your blog visitors to easily tweet about your posts without leaving the current web page. The BigTweet button is similar in appearance to other buttons, but with a very different feature set (uses the same functionality for users as the BigTweet bookmarklet, but in a form which can be inserted into your blog posts).
Flickr Flash Slideshow
Flickr flash slideshow can display a standard Flickr Flash slideshow for a user, set or group inside an iFrame
An update to twitpress by Tom Purnell. Adds ability to select a category that should be posted to twitter.
SimpleMail is a plugin that allows you to access an Email account from your dashboard.
This SEO plugin can handle titles, meta, noindex, canonical tags, 404 monitoring, linkboxes, and robots.txt. Version 1.1 fixes bugs and adds a new post/page title tag mass-editor.
gooseGrade allows your readers to become citizen editors.
The WordPress mailing platform
Posts per Cat
List latests N article titles from all or top level only categories and group them in category boxes organized in two columns.