Samsung's promotion website has a new deal today that might tempt you to finally pull the trigger on that Galaxy S6 you've had your eye on. If you buy the 64GB Galaxy S6 or S6 Edge, Samsung will basically cover the difference between that and the 32GB with a $100 rebate. Samsung calls this the "Ultimate Upgrade." You have until the end of the day on July 5th to make your purchase.
As with most deals of this sort, you'll need to submit a copy of your receipt, the device's MAC address, and the IMEI. It needs to be purchased in the US (sorry, guys) from a carrier or national retailer (i.e. not on eBay or Craigslist). Samsung says it also needs to be purchased at "full price," which I assume means no additional discounts. Presumably you can still do a contract or payment plan with your carrier.
T-Mobile previously offered a double storage promo, but that was handled at the time of sale. The paperwork claiming the rebate has to be submitted by August 5th in order to get the money. You can do everything online at the Samsung promotional website, or mail it in (must arrive by August 12th, postmarked by the 5th).