Vancouver's TinyMassive and Seattle-based WidgetBucks both offer flash ad-widgets that display products from partner sites. Both algorithmically suggest products based on your site's content. Theoretically, presenting an actual product for sale that looks slightly less than an ad will increase click-throughs.
Network: Both ad networks are "walled" and require approval to join. WidgetBucks major partners include Amazon, eBay, Target, Walmart, Best Buy, and Yahoo Shopping. TinyMassive's only major partner seems to be Amazon.com, with a few other smaller partners. But hey, what _doesn't_ Amazon carry?
Attractiveness/Customizability: WidgetBucks' widgets come in 15 different skins ranging from minimalist to tacky, and available in 6 common ad sizes. TinyMassive has 5 sizes, but only 1 skin. It is, however, nice and minimalist and should integrate well with most sites, unless you have a dark background. TinyMassive's widgets have user voting controls to increase engagement.
Money: Both say that their CPC rates depend on "your site's traffic and content". Amusingly, both sites promise the same potential of over $6 eCPM. Your milage may vary greatly, of course. TinyMassive offers CPC + 10% commission on items sold, minimum balance: $10. WidgetBucks has no comission, works on CPC and/or CPM, and requires a minimum balance of $50 for payout. Interestingly, WidgetBucks does CPC for only the US, Canada and UK. Any other country seems to be judged as too spammy and runs on CPM. Both send payments 45 days after the end of the month.
For the moment, TinyMassive seems to offer a better deal, whereas WidgetBucks rates have been lowered over time. The effectiveness of these widgets depends on the audience of your site, and how product-oriented your content is. Any good publisher will try test different ad networks, but I think the magical "$6 CPM" is a dream on either of these networks. Better returns than AdSense... maybe.