If you want a good open-source eCommerce shopping cart solution then zencart is definitely a good choice. It is relatively easy to use for someone with basic development skills and for experts the sky is the limit.
So find your market opportunity and get going. The next areas Towers IT is moving into from an eCommerce market perspective is energy saving light bulbs. We se this as a good opportunity with the new environmental focus and also the incandescent light bulb ban.
However, straight out the box the installation is quite primitive and you will certainly want to use improved templates and image handling tools. Also the URL's are really messy containing parameters and other characters which are neither meaningful to the user or comprehensible by search engines.
The solution is to load one of the SOE friendly URL modules.
The most basis and easy to load one is "Ultimate SEO URL's" but although this is a good step forward it does not offer a high degree of sophistication.
The one I would recommend which I have used on Energy Saving Light Bulb Shop created by Towers IT PS.
is CEON URL's which gives you control to format the URL's exactly as you want them. Just take care to have meaningful and clear navigaction.
This is a great feature both from a user and search engine perspective.