Rather than focus on the technologies involved you'd be better at selling this if you wrote about the features you intend to support.

There are a million and one projects hosted on sourceforge that have grandiose plans to take over the world, and no code to show for it. What makes you think you can do better?

I'm not trying to put you off, or ruin your announcement, but unless you have features and at least a small idea how to do what you want you're going to get nowhere fast - and involving too many cooks at an early stage of the project is liable to land you in a real "designed by committee" mess.

The best thing to do, IMHO, is to define what you want to achieve. Exactly.

There are lots of existing shopping cart systems around - why don't they work for you? What specifically do you need that writing from scratch is better than adding missing features to an existing piece of software?

Whilst you could come up with something revolutionary I'm sceptical based on what you've written thus far - the idea of a stable shopping card that is at the cutting edge of technology seems a little at odds.

How do you plan to handle payment gateways? What do you want to use for the layout? How are you going to handle mutliple languages? All these and more are serious questions which you need to flesh out a little at least.

Supporting mutple databases is good, but you should probalby start with one and add more support as time goes on - too much abstraction early on can be a killer.