A thread at Cre8asite named Where to put the site map link?, discusses the location of the link in terms of page placement and number of pages.
Some suggest in the thread to place the site map link at the top, header, portion of your pages. Some say, place it at the footer. I personally do it differently on different sites. What does it depend on? The layout of the site.
I am a believer of placing the site map link on every single page, not just the home page. In addition, I do not like breaking out site maps into sub site maps. I feel that site maps that have sub site maps are more category, to sub category to sub sub category pages. And thus should be treated as such.