Prior to WordPress 3.3 adding WYSIWYG editor to a frontend page meant you had almost reinvent the wheel. In WordPress 3.3 wp_editor was introduced which made developer/designer’s life whole lot easier. Now you can add the same editor used when you type up a post can be added anywhere in your theme or plugin (frontend or backend).
I stumbled across this function by accident when I was checking why the WYSIWYG editor was not working on one of my plugins on WordPress 3.3 . You also can allow users to upload images if the user has necessary capabilities using the editor wp_editor adds.
Read all about it on the WordPress Codex . Hope someone will find it useful.