Accepting credit cards cost money... monthly usually. Unless you have paypal... they just take a percentage. To some consumers, paypal is a bit of a turn off, but at the same time its a decent learning tool. If you're not sure how to add a shopping cart, they have pretty good tutorials. Also, www.oscommerce.com has decent and FREE shopping cart software, but i've found quite a few glitches as far as accepting credit cards goes.

I wish I had more info for you, but this is a problem I'm currently trying to fix myself, so once I figure out something, I'll be sure to post my solution! Good luck, and please let me know if you have any luck with anything else. I'd like to know.