Stay away form the WYSIWIG ones. That includes the proprietary ones such as Dreamweaver and the many Micro-soft tools for the task. The open source(not all are free software, as defined by the GNU) ones can make a mess of it too, though. Joomla, Open- or LibreOffice can generate some messy or incomprehensible markup as well.

If you know how to do it and have time, you could write your own framework from scratch. That takes a lot of time, though, and you're probably better off using a framework and building off of that. My fellow Monks have recommended some very great frameworks in the writeups above.

Or, if you are extremely lazy, you can just get one of those webhosting subscriptions with one of those "app installers" that will install the shopping cart software(in PHP, almost invariably) for you with "1-click".
But that's for end-users, and quite frankly a waste of your programming skills