WebFactory

Opens external links in a new tab or a or new window. You can set URLs that should either be forced to open in a new window or ignored.
The plugin produces XHTML Strict compliant code and is search engine optimized (SEO). 
This is done using JavaScript’s <code>window.open()</code>-function. It adds only a few lines of vanilla JavaScript to the page, and does not require any external libraries like jQuery.
Most other plugins perform a hack by altering the <code>target</code> parameter (i.e. <code><a href="http://somewhere.example" target="_blank"></code>). That method is not XHTML Strict compliant. 
This plugin handles the links client-side, which lets search engines follow the links properly. Also, if a browser does not support JavaScript, the plugin is simply inactive, and does not result in any errors.
If you need a more advanced plugin, with more options try our <a href="https://wordpress.org/plugins/wp-external-links/" rel="ugc">free WP External Links</a> plugin.
Credits 
Inspired by the <a href="http://www.zappelfillip.de/2005-12-05/zap_newwindow/" rel="nofollow ugc">Zap_NewWindow</a> plugin by <a href="http://www.zappelfillip.de/" title="His website is mostly in German" rel="nofollow ugc">Tom Köhler</a>. 
The banner is a <a href="http://www.flickr.com/photos/monja/1367946568/in/photostream/" rel="nofollow ugc">photo</a> by <a href="http://www.monja.it/" rel="nofollow ugc">Monja Da Riva</a>.
Translations 
Danish by <a href="https://kristianrisagerlarsen.dk" rel="nofollow ugc">Kristian Risager Larsen</a> 
Dutch by <a href="http://www.collectief-it.nl/" rel="nofollow ugc">Paul Staring</a> 
Lithuanian by <a href="http://Host1Free.com" rel="nofollow ugc">Vincent G</a> 
Other translations will be appreciated!
Known bugs 
The plugin conflicts with other plugins that change the links’ `onClick´ attribute.
Original developer 
Kristian Risager Larsen – <a href="http://kezze.dk" rel="nofollow ugc">kezze.dk</a>

External Links in New Window / New Tab

Open external links in a new window or new tab. SEO optimized and XHTML Strict compliant.

Nazmul Ahsan

Codexpert, Inc

Pluggable IO

Force links in posts or pages to open in a new tab. No configuration required.

Target _blank – Force links to open in a new tab

Force links in posts or pages to open in a new tab

External Links in New Window / New Tab vs Target _blank – Force links to open in a new tab