I guess my question would by, why are you creating a sub domain to help your  main domain?  All the effort you are putting into the sub domain, could be put into the main domain for more power.  This is why everyone suggests "www.example.com/blog" instead of "blog.example.com".

Depending on what you are doing, a sub domain or a different tld are going to have the same effect.  (I'm assuming your main domain is www.example.com)

I would suggest reading "Root Domains, Subdomains, Microsites and subfolders" from SEOmoz. http://www.seomoz.org/blog/understanding-root-domains-subdomains-vs-subfolders-microsites

If the site is built well, then all pages would be accessible via 3 clicks. So html sitemaps really aren't needed.

I feel html site maps are no longer needed if you correctly setup XML sitemaps, and also link to them from your robots.txt file.

But if you still want them for users, then I would put it in the footer, and have Google Index and Follow.