This is a cc offer, but seeing as how this is the main churning thread, I'll post it here.
If you need Hawaiian or Alaska miles, there are two separate offers for 70k miles after a single purchase (any amount); one is the Barclays Hawaiian Air credit card, the other is the Bank of Hawaii (issued by Barclays).
Both have a $99 yearly fee, but the miles in your Hawaiian Air account don't go away if you close the cards.
Pretty good deal, 140k miles for $198. I just booked a RT PDX/Maui for 41,500 miles.
There are also tons of great bank bonuses on DOC. I've got $20k in Live Oak and $20k in Chase Business and $10k in Grasshopper, and I'm leaving money on the table by not having more available for other bonuses.