If this hasn't been answered yet, this may be helpful. I just copied the HTML form from the mailman manager page. Using the same form, and hiding all of the optional fields, you can create simple form to put on any page that only requires the email address. Make sure you setup the list in the cPanel first and substitute your list and site where appropriate below.
<FORM Method=POST ACTION="http://somesite.com/mailman/subscribe/somelist_somesite.com
Email: <INPUT type="Text" name="email" size="30" value="">
<input type=hidden name="digest" value="0" >
<INPUT type="Submit" name="email-button" value="Subscribe">
Now for a question about installing and using another mailing list program like Dada mail. If we install Dada mail ourselves and create multiple mailing lists 3 or 4, are we violating any Lunarpages agreements and do we have to pay extra for each list?