Anthony Acosta

Provide visitors to your site the the option of increasing or decreasing the size of text by clicking on an icon which represents larger or smaller text.
Usage is simple. You can insert the code <code><?php if(function_exists('wptextsizerincutil')) { wptextsizerincutil(); } ?></code> where ever you would like the icons to appear.
NOTE: Some text will not resize if it uses an absolute size (pt) rather than a relative size in the CSS. This plugin will only resize text elements within the “content” div tag. If you are not using a div tag called “content” this plugin will not work for you.NOTE: Some text will not resize if it uses an absolute size (pt) rather than a relative size in the CSS.
All the information (general, changelog, installation, upgrade, usage) you need about this plugin can be found here: <a href="http://kennedymedia.com/wp-text-sizer" title="WP-text-sizer Readme" rel="nofollow ugc">wp-text-sizer Readme</a>.
Changes. Original code looks for the CSS “toparticle”, this has been corrected so that it searches for “content”.
<h3>Development Blog</h3>
<a href="http://kennedymedia.com/wordpress/" title="Kennedy Media's WordPress Plugins Development Blog" rel="nofollow ugc">Kennedy Media’s WordPress Plugins Development Blog</a>
Version 1.1.1 Fixes php shortform tags (Special thanks to Peter Fraterdeus for pointing this error out)

WP-Text-Sizer

Provide visitors to your site the the option of increasing or decreasing the size of text onclick of image or text links using JavaScript.

Brad Parbs

wpTextResize is an easy to use way to have Increase, Decrease, reset font size controls for body text on a WordPress site.
Just use the [wpResize] shortcode wherever you want the controls to show up. Or use the widget to place it in a sidebar.
Theme creators: You can also add wpTextResizeControls(0) to your template for the controls to be automatically styled, or wpTextResizeControls(1) to manually style. When manually styling, wpTextResizeControls is the container, and increaseFont, resetFont, and decreaseFont are all anchors you can target.
Go wild!

wpTextResize

wpTextResize is an easy to use way to have Increase, Decrease, reset font size controls for body text on a WordPress site.

WP-Text-Sizer vs wpTextResize