Your question is ambiguous. Every resource has different uses. For instance, you can use Twitter and Facebook branding your products. You can use DMOZ to work on SEO for your website.
In my case, I use Google merchant center and ShopWiki to promote individual items. Also theFind collects information about my products.
Coupon websites are good ones I use. RealMeNot is a good one. I post coupon codes to the site, so shoppers come to my site to purchase items. Hope my answer helps you.