Most Facebook tabs require that you create a Facebook Developer’s Application, and these generally require an SSL certificate and a dedicated IP address (anywhere from $45 on up).
But TabPress is FREE – after installation, just add your HTML code to the interface and voila, you will be up and running in no time. Here is a page with the TabPress Welcome tab installed: Himalayan Gap Year on Facebook.
You can find more information about TabPress here, and the installation page is here. To set the Welcome tab as your default landing page, change the settings on your page (see Edit Page towards the upper right corner of your Facebook page).