I'd second the 'restore from last good backup', but might be possible to hack-attach the database. Last resort though.
http://www.sqlskills.com/blogs/paul/disaster-recovery-101-hack-attach-a-damaged-database/
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability