I'm not sure if you can bookmark items within the iTunes Store or if so, how. But you can drag the title of items to the desktop, where they become clickable URL files that access the items' pages in iTunes via your web browser. If you drop this URL into a text-entry window of various programs, you either see a 'regular' URL or the (clickable) icon of a URL file. Experiment.
Alternatively, you could right/Control-click an item title, select 'Copy Link' from the popup menus and paste it into your browser's address bar for access or bookmarking, or into a text file for alternative storage.
