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!