I'm a bit behind the eight-ball here but hopefully my reply will help others out. Most banks are negotiable with their interest rates - especially if you're a profitable customer they'll bend over backwards. Give them a call and tell them you want to negotiate your credit card interest rate and see what happens.
There is also the Balance Transfer option. Most (if not all) financial institutions have some kind of BT promotion on. Just be careful you don't get caught out with payment allocations and purchases on the card ie any payments made to the card are allocated to the balance transfer which is at the lower interest rate and any purchases made on the card will be at the standard rate ~20% and wont be paid until the BT is paid in full so if it takes you 6 months to pay a BT and have purchases sitting on there for say 4 months, they're accruing interest at the high rate.
Also, with most financial institutes when a BT special rate expires it will convert to the cash advance rate which is even higher again. But, there is nothing stopping someone from becoming a serial BT'er and one expires just open up a new one!