This is a tough category to get a good coupon for. Most margins at these stores are so low that they can't offer much. Look for free shipping specials and discounts in individual items instead of broad promotions or discounts. One way to get deep discounts is to shop some of the clearance places like overstock.com. If you want a lower price on brand new items, watch for sales listed here. Many of the stores listed will over broad sales that cover entire categories of products.
B&H Photo: They have come to be one of my favorite stores. They sometimes offer a promo code for a specific item but more often they offer sales on categories of products. Check them out.
Compact Appliance: This store carries appliances for your home and they specialize in smaller versions especially for apartments.
Sony Style eCoupons: This is one of the places that offers real deals. Codes only apply to a single item but you can get some spectacular deals. They have deals on DVD players, PS3's, digital camera, audio equipment and anything else sony makes.