First, please try to think of better titles in the future. The first words of a sentence don't really signify what the thread is about, and you tend to get fewer responses to poorly named threads (because so many people just ignore them). In this case, I would have suggested "transfer cash advances between cards?" or something like that.

Anyhow, if doing it the striaghtforward route (straight from one card to anothe card, not going through your checking account as described in other posts above), it has to be a card from a completely different bank.

Ie, you can't do a balance transfer from one card issued by Citi to another card issued by Citi, or from one card issued by Chase to another card issued by Chase.

But you can do a balance transfer from one card issued by Citi to another card issued by Chase, or vice versa.

And keep in mind that 0% balance transfers are generally not "free". There's typically a one-time fee (3% to 5% of the amount transfered, often with a flat minimum), independent of the 0% (or whatever low) interest rate. So while you can theoretically extend a 0% transfer quite a while by transferring back and forth between at least two cards from two different banks, the more often you do it the more you're charged in these fees. So if the fee is 3%, and the 0% only last one year, then you've essentially been charged 3% for a year, not 0% for a year. That's still great, compared to "normal" credit card interest charges, but it does mean that 0% transfer money is usually not totally free any more (and should be used with that in mind).

For this reason, a 1.9% interest rate balance transfer that lasts two years and comes with a 3% transfer fee may actually be a better value than 0% interest rate balance transfer that only lasts one year and comes with a 5% transfer fee, if you're going to need to use the latter twice, because then you'll actually be charge more in fees alone than you would be with one fee + interest for two years.

Finally, keep in mind that any payment problems (not paying enough or skipping a payment) will immediately cancel the 0% (or low) interest rate, and jump you into at least the normal interest rate for that credit card, if not a penalty rate. So make sure you can keep up with the payments and the payment schedule with no possible issues if you use a transfer.