Some plugins give you “shortcode” to easily insert items into posts and pages. It’s usually a word or phrase within [ ] brackets that when viewed in the browser, it displays something else, sometimes a gallery or form. For some reason, the “widget” area doesn’t automatically support this type of code. No worries, the cool thing about WordPress, is there’s usually a workaround for this kind of thing.
To allow shortcodes in sidebar widgets, simply edit the functions.php file from your theme and add the following code:
Once you saved the file, you can now add as many shortcodes as you want in sidebar widgets. 🙂
A Thanks to English Mike for this tutorial: http://englishmike.net/2008/07/07/wordpress-quick-tips-3adding-a-shortcode-to-a-sidebar-widget/