Encountering a corruption in a database is a rare thing. It can happen, however, most often due to faulty hardware or operational mistakes (like deleting a transaction log file).
The points below is a very high level of recommendation for handling a situation where you have some type of corruption in a database or if the database goes into suspect status.
What you really want to do next is to check the SQL Server disaster recovery poster.
And here is a great PASS presentation on the subject, by Paul Randal, if you have an hour and fifteen minutes to spare.
SELECT name, database_id, state_desc FROM sys.databases. State will tell you a bit more of what is the problem. You will typically see RECOVERY_PENDING if a database file is missing and hindering SQL Server from performing automatic recovery at startup. For these situations (database file missing), you are likely not able to perform DBCC CHECKDB and if it a log file which is missing you will not be able to perform the last log backup.
DBCC CHECKDB(dbname) WITH NO_INFOMSGS