Ecommerce solutions
If you already Have a site, You maybe try looking at a javascript add on, they are secure as everything happens client side. there is so many available its not funny
just google ".js shopping cart script" or add open source if your looking free
Don't forget if you use it commercially think about donating to them
especially good if you have a small site and you don;t need the bulk of a full cms, that i find are too complex for a lot of clients to run back end...... don;t get me wrong the big cms's are good in the right application