Advanced WordPress Theme Editor
The Advanced WordPress Theme Editor plugin will allow you to edit your theme directly in your blog admin section but with a better experience since it will format and highlight your source code with nice colours.
The plugin is compatible with WP 2.8 and less and is based on the Edit Area script that supports at least PHP, CSS, JS and many more file types.
Download the Advanced WordPress Theme Editor plugin V1.0
For having the plugin running in your wordpress you will only have to upload the unpacked folder into the ‘/wp-content/plugins/’ directory and activate the plugin through the ‘Plugins’ menu.