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I looked into several freely available plugins, the one that got me going was a very simple one, the SlideShare plugin by Joost de Valk. The plugin transforms a formated tag into code that embed a flash player for SlideShare presentation. Below, I reproduce the skeleton of a plugin that will replace the tags in your post/pages/comments for whatever you like. A tag takes the form [tag-mnemonic param1 param2] and the plugin replaces it by just a HTML list of the two parameters.

 <?php
/*
Plugin Name: Simple Plugin
Plugin URI: http://host.org/
Description: Replaces a tag for a list.
Version: 0.1
Author: Xavier Llor&amp;amp;amp;amp;amp;amp;amp;amp;agrave;
Author URI: http://www.xavierllora.net

Based on SlideShare plugin (http://wordpress.org/extend/plugins/slideshare/)

Installation: copy simple-plugin.php to the wp-content/plugins directory of
your WordPress installation, then activate the plugin. Use the following syntax
for your tag

[tag-mnemonic Param1 Param2]

When the plugin is active, the tag will be replaced by a simple HTML list
containing the parameter values.

*/

define("SP_REGEXP", "/\[tag-mnemonic ([[:print:]]+) ([[:print:]]+)\]/");
define("SP_TARGET", "<ul><li>###Param1###</li><li>###Param2###</li></ul>" );

function sp_plugin_callback($match)
{
	$output = SP_TARGET;
	$output = str_replace("###Param1###", $match[1], $output);
	$output = str_replace("###Param2###", $match[2], $output);
	return ($output);
}

function sp_plugin($content)
{
	return (preg_replace_callback(SP_REGEXP, 'sp_plugin_callback', $content));
}

add_filter('the_content', 'sp_plugin');
add_filter('comment_text', 'sp_plugin');

?>

That means that if you write the tag [tag-mnemonic http://foo.org http://example.org], the plugin will reformat the tag and inject the following html code

<ul>
<li>http://foo.org</li>
<li>http://exampl.org</li>
</ul>

where the tag originally was. And that’s it!

One more thing. The only thing you may want to be aware is the filtering chain. The add_filter has a third numeric parameter. When you have multiple plugins that rely on filters to do their job, sometimes you may need to force a certain order of execution to avoid stepping on each others toes. If that is your case, you better check the add_filter documentation. It may save you some time, trust me

PS: Joost had some comments on improving this simple plugin. Check the comments below

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WPhone allows you to use a custom admin interface while interacting with your WordPress install via your phone. It contains two versions of the mobile admin interface:

• an iPhone / iPod Touch specific interface with full Javascript and animation support 
• a lightweight, simple version designed for all other phone types (no Javascript or anything else required)

WPhone, while stable, is a work in progress. Many more features are already planned and will be coming soon in future versions.

This plugin is designed for use with the latest version of WordPress, but will work with versions 2.1 and newer.

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