CG-Amazon works with 2.1 from my own testing, though I’m using a version of code beyond my last public release. ?? The advantage over WP-Amazon is it doesn’t embed ‘fixed data’ into your post, just a tag with an Amazon ASIN product code — which is resolved into a live lookup later (along with formatting). Means you can globally adjust formatting.
It also does very nicely for ‘now reading’ type lists for sidebars, having it’s own internal category system and personal ‘product database’.
The power doesn’t end there — those are just the quick and easy things. It can be used to build a mini shop off your blog (well, more of a product ‘catalog’ at the moment), and can be talked to directly for keyword-based product queries, or other customized lookups.
As Otto notes, depends on what you want it to do (and where!). ??
-d