There are a couple of relatively simple and inexpensive ways to go about it:

1) Register your CD(s) at CD Baby. (Instructions are at http://www.cdbaby.net/submit.htm ). There are some charges (a setup fee of $35, then they keep $4 from every CD sold, last I checked), but it's very convenient since they take care of all the shipping. Once you set it up, I'll just put a link to your cd baby page on your site.

2) Sign up for a Paypal account (www.paypal.com). This will allow you to accept credit card payments online. Paypal will charge you a small percentage for each transaction, then you ship the merchandise yourself. You can sell anything you want (CDs, DVDs, T-shirts, whatever) and specify the shipping-and-handling amounts.

Those are the quick-fix solutions. If you're looking to establish a full-fledged e-commerce site, I can do that, too, it'll just cost a lot more.