The Ping-O-Matic plugin pings http://pingomatic.com/, from where your ping gets relayed to a set of most common ping services.
Adds a toolbar on top of the post editor for easy HTML tag inserting.
The Generic ping plugin can be used to add a generic RPC ping service to your blog.
The Wacko is a simple renderer plugin that provides Wacko style formatting. This allows to easily create different markup/formatting, even on blogs that do not allow HTML.