Blogspace is certainly abuzz about iTunes4 and the Music Store. This article nicely summarizes how URLs to specific parts of of the Music Store are structured. If you want to see what the URL delivers, just change the "itms" to "http" and your browser will display the returned XML document the best it can (bad in Safari, pretty good in Mozilla and IE). One thing you can do with the XML is copy the URLs which point to the preview files (which are DRM'd AAC files, just like the full tracks) and download the preview files (the URLs are regular http).