Get your OWN online shop

Hey peoples


I would like to have a nice discussion in this thread of how to manage it to have your ownOnlineShop.

This should be for people with intermediate understanding of web programming.
I see the main problems that need solution are:

How to customize your shop?
How let people register?
How to accept payment?


What system would you use to start with?
Would you build your own from scratch or modify the source code of a free shopping system?