The received wisdom of personal finance bloggers and other "experts" is that part of good money management is to have an emergency fund consisting of enough money to get you through 3-6 months with no income. This, to me, does not make sense as good advice to give someone who is paying off revolving debt, especially credit card debt or anything else with similarly high interest. Why do I think this is a bad idea? Simple:
You are borrowing your emergency fund.

Even if you have a fairly small, say $1000 emergency fund, much smaller than the generally recommended 3-6 months, it is still costing you the difference between you debt interest and your savings interest. If you have 30% credit card - hardly unheard of - and a phenomenally good 2% savings account, you are paying $280/year to maintain that emergency fund. That's a lot of money. Even with a pretty good credit card at 15% it's still $130. More reasonable, but still...are you getting $130 in value off of that $1000? And the nice thing about revolving debt is that it's totally unneccessary.

If you were to put that $1000 toward the credit card and an emergency (that would be helped by having $1000) came along, you can always borrow it again. In the meantime, you will have paid off more debt than you otherwise would have because you would have put more money towards principle and less towards interest.

There's only two situations where I can see an advantage to keeping the emergency fund. First is willpower related - if you start borrowing again due to the emergency, it could crack your fiscal discipline and lead to more borrowing for non-emergencies in the future. If you think this is a problem for you, personally, then maybe an emergency fund is for you. The second is if you are paying down non-revolving credit. If you're trying to accelerate payments on a hospital bill, mortgage or student loan, you cannot readily re-borrow that money in a time of need, so having an emergency fund may make sense. An alternative to the emergency fund, though, may be to set up a line of credit for emergency use. I have a $5000 line of credit that costs me nothing if I don't use it, and only costs the interest - no fees - if I do use it. So if it dips into the red a couple times a year, costs it costs me a few dollars, but nothing substantial. It's tied directly to my chequing account, so I only pay interest on the amount of the shortfall, and only only for the few days until I get a paycheck to return me to a positive balance (I've never let it get so low that a single paycheck won't take care of it).

So, do I advocate not saving at all until you are debt free? No, not exactly. I favour a system of purpose based savings. Save for retirement, save for a down payment on a home, save for a new computer or a vacation. Why? Well, it's about my own psychology and so I suppose that it doesn't really apply to everyone. I keep these savings funds because I would not borrow money to go on vacation. But if I save up for it, I will go. From a purely mathematical perspective, I would be better off paying down my student loands, and then borrowing against my line of credit for this niceties. But I wouldn't, the difference is sufficient in my mind to allow me some of the finer things in life through this method.

But emergencies are different. In an emergency I would need the money, so taking on debt wouldn't be a choice, it would be a requirement. That's not a problem. Better to maybe have to pay interest down the road then certainly have to pay interest today.