Your best bet for getting an exchange up & running quickly/cheaply would be to fork buttercoin:
https://github.com/buttercoin/buttercoin
It's an open-source crypto exchange.
Thanks. It may sound a bit jammy that this site has inspired me. It would be woefully naive of me or anyone embarking on such a task in establishing an alto exchange given the post-Mt. Gox environment to take the responsibility of others money, lifely hood and financial well being without the most critical attention to detail. Mt. Gox is just the tip of the iceburg for what will surely be the continuation of larger hacking and system attacks. The shear monumental task of trying to mitigate what the "Dark" (pun intended) forces of human greed and villainous nature can never be underestimated. Thus why really DarkCoin must be made...to protect ourselves from those that would strife to strip us our "property". The building of an exchange must take these realities to heart. I'm wondering if something like this could be partially funded by crowd sourcing?
I think you just wrote the opening pitch on the kickstarter page...