Amazon is known for offering deep smartphone discounts on a normal day, so when the retail giant announces a special holiday sale, prospective smartphone buyers would be wise to check it out. In celebration of Memorial Day, AmazonWireless is offering sale prices on nearly 20 4G smartphones. Highlights from the Memorial Day weekend sale include the Samsung DROID Charge for $179.99, the LG Revolution for $149.99, the HTC ThunderBolt for $129.99, the Samsung Infuse 4G for $129.99, the T-Mobile G2x for $99.99, Sprint’s Google Nexus S 4G for $49.99 and the HTC Inspire 4G for just $0.01. All prices are on contract, of course. Amazon is also offering a few other incentives, a $10 Amazon Appstore credit for students when they purchase of an Xperia PLAY between now and June 4th, and a $25 Amazon gift card with the purchase of any Windows Phone starting May 30th.