For example, you may want to welcome Diggers with a message that reminds them to digg your story, or you may want to ask Del.icio.us users to bookmark your post, and so on.

The plugin is easy to use and install. It comes with out-of-the-box support for 14 sites which should cover a good portion of the traffic that you would receive.

This makes it a install and forget plugin unless you really want to bother about customizing it.

Referrer Detector has many useful features like pure AJAXed admin  interface,  the greet box position option, or you can put a tag (<?php if (function_exists('referrer_detector')) referrer_detector(); ?>) into the template to show the greet box anywhere of choice. Exclude URLs, a stat panel. Many installed-by-default entries (which can be restored anytime with one click). Upon installing, you will have these entries available:

• 9 rules
• Del.icio.us and Delicious.com
• Digg
• Gizmodo
• Google Search
• Lifehacker
• Live Search
• Reddit
• StumbleUpon
• TechCrunch
• Technograti
• TechRadar
• Twitter
• Yahoo Search

2nd Plugin is ‘WP Greet Box‘.

This plugin lets you show a different greeting message to your new visitors depending on their referrer URL.

For example, when a Digg user clicks through from Digg, they will see a message reminding them to digg your post if they like it. Another example, when a visitor clicks through from Twitter, they will see a message suggesting them to twit the post and follow you on Twitter. You can also set a default greeting message for new visitors (not matching any referrer URLs) suggesting them to subscribe to your RSS feed.

Having these targeted suggestions will help your blog increase exposure, loyal readership, and reader interaction.

Its prominent features are,

• Show a different greeting message to your visitor depending on the referrer URL. You can add/edit/delete/disable these greeting messages as you choose.
• Greeting messages automatically get inserted into the top of your posts upon activation. There is no need to modify theme files.
• Ability to auto-insert greeting message to the top or bottom of the post.
• Greeting messages can be user closeable or not.
• Ability to detect the visitor’s search keywords from major search engines and automatically display related posts under the greeting message.
• Show a default greeting message even if the visitor does not match any of your configured referrer URL.
• Show a default greeting message even if the visitor does not have JavaScript enabled.
• AJAX greeting message in the frontend makes it compatible with caching plugins (such as WP Super Cache) and WPMU.
• AJAX administrative interface that uses nonce verification to discourage hackers.
• Ability to set a timeout to forget a visitor so we do not keep nagging them with greeting messages.
• Ability to set rules to exclude some referrer URLs from seeing greeting messages. Regular expressions is also supported (but not required!).
• Ultra customizable greeting message box (with CSS) allowing you to prefix/append HTML around the greeting message box.
• Currently the following referrers are installed by default, but you can easily create your own if your favorite referrer is not on the list!
  • blinklist.com
  • blogmarks.com
  • del.icio.us
  • delicious.com
  • digg.com
  • diigo.com
  • facebook.com
  • flickr.com
  • furl.com
  • google.*
  • ma.gnolia.com
  • mister-wong.com
  • myspace.com
  • netvibes.com
  • newsvine.com
  • reddit.com
  • search.live.com
  • search.msn.com
  • search.yahoo.com
  • simpy.com
  • stumbleupon.com
  • technorati.com
  • twitter.com
  • youtube.com

My personal review is that I prefer ‘WP Greet Box‘ and I’m using this plugin at one of my sites. The ability to display related posts make it better then Reffer Detector.

Are you using any of these plugins? Or anyother greeting plugin? Has it helped increase visitor loyalty, number of hits? Please tell us about your experience through comments.