One solution often mentioned on this group is
www.candypress.com
If you want a custom solution, you will need to write the server side code
(in scripts such as PHP, Perl, ASP or .Net) which can be complicated if you
are not a programmer.
Other solutions I suggest are:
Paypal -
Create an account and use their merchant tools to create "buy now", "add to
cart", "view cart", "Checkout" buttons. You make a normal html page, and
then in paypal's site, go through a 'wizard' online form filling out the
options you want for each product listing, then it generates the <form> code
for each item (so that it can integrate with PayPal's shopping cart and
payment processing features)
Using PayPal, you have a ecommerce capability set up fairly quickly and
easily, without having to worry about the issues concerned with privacy and
security (if you plan to accept credit card payments) - Paypal does all the
CC processing for you.
There are of course other similar ones out there like authorize.net etc.
It's up to you to use one or the other or even both.
Paypal's site also lists third-party shopping cart scripts that integrate
with Paypal, so you might find a solution there.
Aside from paypal, I've used in the past
http://www.oneworldstorefront.com/. Not a bad application, and integrates
well with Paypal too. Although it is a "pay for" product, you get the
ASP/MS Access version free for one domain, and for all extra licences pay
the fee for each, but they also have mult-licence plans that work out
cheaper than buy single liences as you go. e.g. one single licence is
$29.00; 5 licences is $120 (working out to $24 each).
There is also an ASP/MS Sql version for more robustness and stability.
