SPG already has some pretty good deals when flying with Delta, and even offers some benefits to Platinum SPG members for Delta miles as well. The current program is called crossover rewards. This program allows SPG members to earn SPG Points for flights on Delta Airlines. Platinum members also earn Delta miles when staying with SPG. This program has even been extended to work with Emirates as well.
Today SPG sweetened the deal a little bit. Now with the new Double Up promotion, you don't have to be a Platinum member with SPG to earn Delta miles for staying at Starwood properties. The new promotion runs through the end of June and applies to all SPG members, no matter their elite status.
How this promotion works is that you need to register at the above link providing your Delta Skymiles account, your SPG account and your SPG email. Doing this will allow anyone staying at a SPG property in the US and Canada to earn 2 Delta miles per $1 spent at Starwood hotels.
Personally this is a great promotion. Starwood is my preferred hotel chain, because of their insanely good rewards program. I already have 2 stays planned in the US before June 30th, and that may expand depending on how things play out in the coming months. Now I can boost my Delta Skymiles account for stays that already had been planned months ago.
Also remember that this promotion stacks with promos already running. For instance the double Starpoints promotion is running now that gives 2 extra Starpoints per dollar spent on any hotel stay. Also included in that promo is an extra 250 points per night at participating hotels. This just compounds with the new Delta promotion to add up to a whole lot of extra points all at once.
Just keep in mind that this promotion is limited to properties in US and Canada, sorry for those on international stays other than Canada. Make sure to go sign up and get some extra mileage out of your stays!