Anyone know the answer to this? For example, lets say I have a card with 15% interest on purchases and 20% on cash advances - if I get hit with a $30 over the limit fee, would this accumulate interest at 15% or 20%? (or higher?)

Any thoughts?

If the over limit charge results from a purchase, I guess it should be treated at a purchase rate, but all the over limit charges and fees need to be pay back at once. For more information try Credit Card Offers information site.

It depends on the credit card. Read the terms and conditions that come with the credit card.

If you are going over the limit, you seriously ought to think about budgeting your spending better in the first place.