Among the bargains are a 50 percent markdown on the Amazon Echo, $50 off the August Smart Lock, and 30 percent off select Under Armour apparel.
And with all the buzz, rival retailers are not about to sit on the sidelines. Instead, they are hoping to capitalize on the heavier-than-normal shopping traffic online this week, too.
"We are seeing other big box retailers use Prime Day as an opportunity to capture shoppers' appetite for deals and as way to compete against Amazon for share of wallet and mindset," PwC's Consumer Markets lead Steve Barr told CNBC.
"But the only way they will draw attention away from Amazon is through great deals," Barr said. "July is becoming equivalent to November with month-long discounts to entice shoppers."
This year, Amazon extended the length of its event to 30 hours, with new deals being featured on Amazon.com as often as every five minutes, the company said. Deals will be organized by so-called most-shopped-for themes. Additionally, Prime members can download Amazon's app to learn about deals up to 24 hours before they go live.
A survey shows 76 percent of Prime Day shoppers visit other major online stores to research product ratings and reviews before making a purchase on Amazon, according to consumer research firm Bazaarvoice.