Delta SkyMiles Flash Sale: Cheap Roundtrips to Mexico & Caribbean

Delta has put many routes between the US and Mexico/Caribbean on "sale" right now through September 5, 2018 (this coming Wednesday). I say "sale" because Delta doesn't have a published award chart anymore, but we know from charts maintained by people like us online that the standard lowest level US > Mexico and US > Caribbean award price is 17,500 Delta miles one way.

Delta Flash Sale: 80k Roundtrip in New Premium Select Cabin to Asia

Through August 16, 2017 (tomorrow) at 11:59 PM ET, you can book roundtrips between the United States and Tokyo, Seoul, and Beijing in Delta's new Premium Select Cabin for 80k Delta miles roundtrip, or 65k roundtrip in economy.

Delta Flash Sale: 20k Roundtrip Domestic Awards

Through July 12, 2017 (tomorrow) at 11:59 PM ET, you can book roundtrips within the United States (on select routes) for travel September 6 through October 31, 2017 for only 20,000 Delta miles.
Sale Routes
Delta states that the sale applies to award flights with the following origins/destinations:

Washington, DC
Jackson, WY
Bozeman, MT
Idaho Falls, ID
Reno, NV
Phoenix, AZ
Knoxville, TN
Philadelphia, PA
Boston, MA
Salt Lake City, UT
Rapid City, SD
Las Vegas, NV
St. Louis, MS
San Antonio, TX
Buffalo, NY
Sacramento, CA

Flights don't need to be direct.

Delta Flash Sale: 110k Roundtrip in Delta One to Europe

Through March 15, 2017 (this Wednesday) at 11:59 PM ET, you can book roundtrips to Europe in Delta One for travel August through October for only 110,000 Delta miles. The standard price is 140,000 miles roundtrip.

This isn't a particularly earth shattering award price to Europe in a flat bed. You can fly United or American's Business Class for almost the same price any time you can find award space (price is 57,500 United miles or 57,500 American miles respectively).