Delta is giving a 100% bonus when you buy Skymiles for yourself or transfer them to someone. You can now buy miles now at effectively 1.75 cents per mile (with a 2000 mile minimum) plus 7.5% tax. Miles can be transferred for .5 cents per mile plus $30 for the transaction.
You can only transfer a maximum of 150,000 miles from your account.
Offer is good through September 30.