From their FAQ:
If you would like to close your HubPages account, please sign in to the account that you would like to close, unpublish all of your Hubs, and send an email request via http://hubpages.com/email/help/close with the subject “close my account” and the username of the account you would like to close in the body of your message.
URLS:
http://hubpages.com
Please note that AccountKiller.com is not associated with the business listed on this page. AccountKiller provides easy-to-understand instructions and guides on how to cancel charges and relationships from the list of businesses on our site, we have no affiliation with these businesses.