What kind of sitemap are you referring to? If you mean a Google Sitemap in the XML format that Google will read to potentially help them index your site (and which the other major search engines, Yahoo! and MSN, have agreed to support), support for this was added in v8.2, see:
http://www.shopsite.com/help/8.3/en-US/ ... tures.html
If you mean an HTML sitemap that your human shoppers might look at to help them find pages on your site, maybe you could do that will a special custom template or something. I haven't actually done this myself, so I couldn't say.
-Loren