Twitter button plus is nice and useful tool to show Twitter tweet button on your website.
feedHi 4WP allows you connect your blog to your social media, for publishing automatically your news and join themed broadcast groups.
Add Social buttons to your WordPress website.
Add a Twitter "Follow" and "Like" buttons to your WordPress website.
Connect your WordPress site to Buffer and share/re-share your old and new Posts/Pages/Custom Post Types to all major Social Media Networks
This plugin allows site owners to automatically schedule and reshare their content on Twitter and increase social traffic without lifting a finger.
Plugin to share about your old posts on twitter, facebook, linkedin to get more hits for them and keep them alive.
Plugin that automatically tweets your old posts (including custom posts) which helps you increase the traffic on your website.
Twitter Widget with Tweet Reach: Shows latest tweets for any keyword or, your handle along with Twitter Reach.