How can I add a menu item which links to their sites homepage?

Hi

Is there a way I can add a menu item which will take a subdomain owner directly to the home page of their subdomain? I'm not sure how I could do this as obviously the subdomain is going to be different every time, but I need somewhere for them to be able to easily find the name of their site, in case they forget or need a link to send their potential customers to.

All I know is it's going to be Link removed at members request, just never know what the 'something' part is going to be until each site is created!

Thanks

Sally