Additional fraud protection is available for free by numerous card issuers and financial institutions, though most require a little investigation or enrollment. For example, the Verified by Visa program sets up Visa cardholders with an additional password they can use to shop at participating online merchants. MasterCard SecureCode works similarly. It requires the user to enter the correct PIN during checkout at a participating online retailer.
Another option: Try one-time or "virtual" credit card numbers, which are offered by some banks such as Citibank and Bank of America. These numbers are used for only one purchase and then are no longer usable -- so you don't have to worry they'll be swiped and reused by a fraudulent user.
You can also minimize debit and credit card fraud by making use of free account alerts, which notify you when certain transactions or changes occur, such as a transaction for more than a certain dollar amount or a purchase made overseas.
Check your bank or card issuer's site to find out whether they participate in these programs and services.