If you want to earn some bitcoin/cash then you can make proposals of any ideas you may have to me and if you can develop them I will happily fund it. Our key areas of interest right now are decentralized systems of communication and distributed trustless storage systems, some starting points for background research could be POND and also for storage Tahoe-LFS is a very good foundation. In the coming months the next generation of hidden services will be coming about and so much of our own research into theoretical attacks and weaknesses in the network is focused on that and sadly we are struggling to lend a hand in expertise to such projects. We have already taken on some freelance developers who are working on better bitcoin mixing systems and other tools to help improve the anonymity of users. Making a new market software however I do not personally believe will work, Silk Road has a strong brand and when yo make it easy for people to set up their own market then it will also make it easier for scammers. Anyone intending to set up another market must be able to not only create their own market but be able to ensure it is secure which extends far beyond just the source code, I would go as far to say that is only where 20% of the security work goes.