Through July 26, Delta is offering 2500 miles each way (no roundtrip required) on the Delta Shuttle between DC, New York, and Boston. Registration is required, and all standard paid fare classes qualify (even L, U, and T fares).
That’s 5000 bonus miles roundtrip, and I’m seeing weekend fares under $150. Since it’s “per segment” a shuttle flight in conjunction with a longer itinerary should count, at least that’s my read, so (especially if you live in a shuttle market) you may want to add connections onto your larger Delta itineraries to include shuttle flights.
Sadly, for those with Northwest elite status, you’ll need to credit to a Delta Skymiles account in order to earn this bonus.