Here's the latest, rewritten incarnation of my rvw! tool for posting reviews to del.icio.us.
The search part works in any browser, but to be able to actually post the reviews you need a recent version of Greasemonkey and this user script installed (this is necessary for the cross-domain XMLHttpRequest post to del.icio.us' API, rather than messing with Firefox's security settings).
Update: posting should now work in other browsers too.
Update: editing the user script also allows you to add new personalised items to the Rating menu (a few examples are included, such as 'currently reading' or 'to buy').
Notice also that you can use this page as a handy tool for searching Amazon catalogues in different countries - the title for each item is linked to the appropriate Amazon page.