See a clickable page about the current measures here.
The next step for the anti-SSM one is to go before the next session of the legislature. If it receives 50 votes (a quarter of the General Court), it must do so again in the following year to get on the 2008 ballot.
The text of the proposed amendment is:
This proposed constitutional amendment would require the state and local and county governments to license and recognize only those marriages that are between a man and a woman. It would prohibit future same-sex marriages, but would allow continued recognition of those entered into before the adoption of the proposed amendment.