A token is now available on the NXT asset exchange that can be used to buy/sell ethereum BEFORE the genesis block is released. Once the genesis block is released, owners of this asset will be able to redeem their tokens for ether on the ethereum network (or continue to hold, if they wish to do so).
We have purchased some ether in the official presale to facilitate this market. If there is enough demand, we will create more assets by utilizing additional ether bought in the presale.
The asset can be found at this link:
http://www.cryptoassetcharts.info/assets/show/266More detail on the operation, management and ether redemption are forthcoming.
Happy trading!