Eduardo Reveles

Convert the following formats:
<ul>
<li>@username -> http://twitter.com/username</li>
<li>@username/listname -> http://twitter.com/username/listname</li>
<li>#hashtag -> http://search.twitter.com/search?q=%23hashtag</li>
</ul>
It comes with some options to configure, like use nofollow attribute, open on a new page and choose where you want the links to be replaced.

Twitter Highlight

Convert twitter usernames, hashtags and lists in pages, posts or comments to a twitter link.

Stephen Pickett

ThinkTwit is a highly customisable plugin that can output tweets from multiple users (something that very few other plugins can do successfully), #hashtag or keyword. It uses the Twitter Search JSON API v1.1 to access tweets which can be cached. It is very simple, yet flexible and easily customised. It can be placed on your WordPress page simply through drag and drop on the Widgets interface or through the use of Shortcode or Output Anywhere (PHP function call). Supports i18n!
Support: http://www.thepicketts.org/thinktwit/ or on Twitter @stephenpickett
Features:
<ul>
<li>Can be configured from Widgets settings (if displayed in sidebar)</li>
<li>Can be implemented using shortcode or Output Anywhere (PHP function call)</li>
<li>Contains default slimline CSS for integrated look and feel (can be turned off)</li>
<li>Easy to configure and customise (through settings and CSS)</li>
<li>Multiple instances can be deployed (like other widgets/plugins)</li>
<li>JavaScript is not required (unless no-caching is activated)</li>
<li>Can specify multiple usernames</li>
<li>Tweets can be filtered by #hashtag or keyword</li>
<li>You can select to filter between an AND or OR filter to either show tweets only containing specified usernames and hashtags or any of them</li>
<li>Can specify maximum number of tweets to display</li>
<li>Can specify maximum number of days back to display</li>
<li>Supports no-caching, to prevent caching of tweets by caching engines such as WP Super Cache</li>
<li>Supports cURL as a fallback method, if necessary</li>
<li>Supports optional caching of tweets and avatars</li>
<li>Cache can be manually cleared and will automatically update if the cache is empty</li>
<li>Can display the avatar of the Twitter user</li>
<li>Output can be filtered (using apply_filters)</li>
<li>Can optionally output “Follow @username” links</li>
<li>Automated cleanup process that runs periodically according to user setting</li>
<li>Internationalised using i18n meaning that if it isn’t in your language it’s easy to translate! See Other Notes for more details</li>
<li>Gracefully deals with Twitter errors and adds them to the PHP error log</li>
<li>Supports live updates of tweets when using no-caching (AJAX)</li>
</ul>
Requirements/Restrictions:
<ul>
<li>Works with WordPress 3.2 to 5.7.2, not tested with other versions nor re-tested on older versions than most current</li>
<li>Can be installed using the widgets sidebar</li>
<li>Can also be used via shortcode or Output Anywhere (PHP function call)</li>
<li>Uses Twitter REST API v1.1 Application-only authentication and therefore requires an application key (see installation)</li>
</ul>
I am looking for more people to translate ThinkTwit in to other languages, if you are interested please see “Internationalisation (i18n)” 
under “Other Notes”.
<h3>Uninstall</h3>
To uninstall simply deactivate and then delete through the Plugins admin interface. All options and files will be automatically removed.
<h3>Internationalisation (i18n)</h3>
Currently the following languages are supported:
<ul>
<li>es_ES – Spanish in Spain (many thanks to <a href="http://www.webhostinghub.com/" rel="nofollow ugc">Maria Ramos</a> for contributing)</li>
<li>en_GB – English in Great Britain (default)</li>
<li>sr_RS – Serbian in Serbia (many thanks to [Ogi Djuraskovic] (http://firstsiteguide.com/) for contributing)</li>
</ul>
If your language is not listed and you would like to translate in to your language please do the following:
<ol>
<li>Navigate to thinktwit/languages and take a copy of thinktwit.pot.</li>
<li>Open in the language editor of your choice e.g. <a href="http://www.poedit.net/" rel="nofollow ugc">POedit</a>.</li>
<li>Translate each line until you’ve done them all.</li>
<li>Save as thinktwit-lang_COUNTRY.po e.g. thinktwit-en_GB.po – see <a href="http://www.roseindia.net/tutorials/I18N/locales-list.shtml" rel="nofollow ugc">List of all Locales</a> for more.</li>
<li>Go to <a href="http://www.thepicketts.org/contact/" rel="nofollow ugc">Contact</a> and fill in the form appropriately.</li>
<li>I will get in touch and ask that you respond with the translated file and a link to your site (if desired).</li>
</ol>

ThinkTwit

Outputs tweets from any Twitter users, hashtag or keyword through the Widget interface. Can be called via shortcode or PHP function call and supports  …

Twitter Highlight vs ThinkTwit