At this moment in the US at least Bank of America, Discover, Chase, Citi & Capital One have publicly available offers for cards with 15 - 18 months of zero interest. All but the Chase (Slate) & Citi (Diamond) offer rewards of 1% back or better.

It is very common to get a credit limit in the range of $10-20k on these cards, one could easily put all expenses on a 0% interest card, make minimum payments and put the amount of the statement balance in a high yield savings account until the promotional interest ends.

In total one would get negative interest in the amount of the rewards (say 1.25% average) plus the 15+ month yield on the cash stored away.