This is an interesting project. However p2p trade systems have cost; that is the cost of protecting from double spending. Either you have a distributed verification network (like bitcoin with the block generation), or you have some sort of trusted centralized user that 'clears' the trades... (this is normally called a 'clearing house').
If by some miracle you have come up with an algorithm to solve this problem in a distributed p2p manner; it would be wonderful if you could produce a white paper that explains how you propose to solve this doubble spending problem.
I'm working on the Open Transactions project; this project is building secure (and centralized, but to a server of your choice, in the future we can have a group of federated trusted servers); the market software executes in a similar mechanism to the Bitcoin scripting. (through the use of cryptographic market contracts).
I really hope the best for your project, except I'm really scared if it doesn't have the well-thought-out cryptographic foundations (that we are still working on for the Open Transactions project); you will be opening your users up to easy scamming.
Thank you for your response! At first I didn't want to create a new blockchain because I felt there are already so many and it would only complicate things. But now I'm thinking it may be the only possible way to do this securely without a web-of-trust. We are currently designing an algorithm for this. At the moment we're calling it P2Coin. Both me and the one coder for this project that I have so far are working on it. We both enjoy and are good at designing these types of systems. This will be a fun experiment!
I will also advise that no one trade any amount that would really hurt them if they lost it until it is announced as a stable system. Due to the nature of what's at stake here (people's money) there will be extensive testing involved.
All Best,
Michael