Michal Ozogan

This plugin fetch all tweets from Twitter, which has been written about some of your posts. For new article are changes cheching every hour. For oldone it is question one or two days.
You can set how many tweets to show and in swich format. It can be regular HTML or embed tweets generated by Twitter javascript.
List of tweets is automaticky show above comment form, but your can also do manually by put funciont <code><?php tmip_show_tweets() ?></code> into your WordPress theme.
Just remember, Twitter allow to search tweets only few days old, so i will show probably only in new articles. Be patient.

Twitter mentions in posts

Show tweets about your posts right under them.

Raulanton

This ultra light-weight plugin send a customizable notification email to each user/author mentioned in a comment.
Mentions: A mention is an username preceded by the mention qualifier.
Username: This plugin will look for the username in display_names and logins. Multiple authors could be mentioned in a comment.
Qualifier: Can be a character but also a string. 
The default qualifier is ‘@’ to work as in Twitter, but it could be changed via admin menu to be ‘#’ or even an string like ‘Mention:’ .
Email:
The email can be customized to include or not the whole comment in wich the mention is. 
The email can be customized to add a reference to the mentioner profile at the site. 
It is also possible to define email header and footer. 
The email can include the URl to the comment in which he/she was mentioned
I18N:
This plugin is I18N (es_ES, en_US, fr_FR) 
Any help with translations will be nice!

Email Mentioned

Email Mentioned is a lightweight customizable -no coding needed- plugin to send an email to each user mentioned in comments.

Twitter mentions in posts vs Email Mentioned