Is that supposed to be a joke? MPEx is a scam site that is about to be shut down by the FBI. All the volumes on their are manipulated and users are leaving it in increasing numbers. The owner is being actively investigated by the SEC - it is a matter of time before he is extradited.
There's a good troll, then.
OP - minerpart is clearly butthurt and not interested in helping you. I agree with Peter Lambert's advice, MPEX seems to be the most robust but also the most difficult to list on (for good reason). Havelock isn't terrible, but you will also have to go through some stringent due diligence questioning (on IRC at least) if you want to list. As with any business, you'll need to establish some sort of personal reputation and get listed in the Bitcoin-OTC Web of Trust on IRC (and have some reputation!) before any serious investor will look at investing.
If you are happy being labelled a scam and raising a few pennies only to run away with them, I strongly suggest the various smaller
scamstock exchanges such as CryptoStocks, PicoStocks, and BitcoinBourse. If you like the idea of not complying with any regulation, making scamming extremely easy, I strongly suggest you look at the crazy bullshit that is BitShares and CounterParty. Have fun, and let us know what prison is like if you decide to go this route.