MBNA has improved the terms on its balance transfer credit card, offering a market-leading 0% interest on balance transfers for a full three years.MBNA is now one of six providers offering 36 months 0% interest on balance transfers. The others are Bank of Scotland, Barclaycard, Halifax, Lloyds and Virgin Money. MBNA now also offers a similar card through its fluid brand.There's a 2.48% balance transfer fee with the MBNA card (2.79% for fluid). The cheapest balance transfer fee among the leading best buy providers is 1.99%, from Barclaycard.Most of the top providers only offer 0% balance transfers between credit cards, though these new products also allow 'money transfers' (the ability to take cash from your credit card and pay it into a current account) that allow you to clear other debt, such as overdrafts or even a personal loan.MBNA and fluid offer a shorter, 20-month term at 0% interest for money transfers and there's an initial fee of 4% of the balance. The only other best buy for balance transfers to accommodate 0% interest money transfers is Virgin Money, which also has a 4% fee.The APR for the MBNA and fluid cards is 18.9%, matching the other leading providers. However, don't use the cards to withdraw cash as you'll be charged a 5% fee (min £5) and interest of 27.9%.Interest-free deals are rising in popularity, with the UK Cards Association recently estimating there is no interest due on 41% of outstanding credit card debt.