Comment-Emailer allows you to customize the email wordpress automatically sends when a new comment, pingback or trackback has been approved.
Follow Self Pings
Pingcrawl adds a "Possibly related posts" capability by querying Google Blog Search for post tags and pinging the results. Limits are configurable.
This plugin will add avatars of comment-authors to the comment-feeds of your WordPress-Blog.
This plugin collects the comments you posted on other people's websites and lets you display them on your own blog.
FeedBack is a standard inspired by PingBack, and designed to establish relatively secure push mechanisms for feed sharing and management.
Show your comments on other blogs.
Show the Trackbacks Shot
A plugin to help separate trackbacks and pingbacks from comments.
Parses the content of pinged pages looking for the hReview format to supply better information on the opinions of the author.
Easily separate comments from trackbacks and pingbacks
Kramer will add inbound links to a post on your weblog as pingbacks by checking Technorati and by monitoring incoming referrers.