(did a search, etc)

DL has a share-miles bonus going, good until 12/31:

https://dn.delta.com/skymiles/purchasemiles/transfer/landing?region=us&lang=en

$0.01/rdm, + $30 fee. 150k give limit, 300k receive limit, 30k transaction max, 50% bonus to the receiver, bonus posts in 24 hours.

AA is having a buy/gift/share bonus, yet they have a 100k give/receive limit, a 25% bonus, and the giver gets the bonus (not the receiver, as with DL).

There's also a buy bonus, yet at $0.028/rdm, ouch.