Under the CARD act a credit card company must give you 60 days advance notice prior to raising your rates.
What can you do about it if they do?
You can close your account. They cannot raise the rates on the balance if you do this.
You can stop using the card. Only the new charges can be charged the higher rates.
If you stop using the card, just keep it and pay it off as you go, you will maintain the available credit, which is good for your credit score.