While searching for something in BOL i've accidently stumbled onto this little cool command line utility

TableDiff.exe is a table comparison tool that comes with the sql server.

It's installed on the server in the:

"C:\Program Files\Microsoft SQL Server\90\COM\TableDiff.exe"

if your SQL Server is installed in the program files on c: drive.

Example use:

This compares 2 tables in the same database on the same server and creates a new table called DiffsTable that holds the differences:

"C:\Program Files\Microsoft SQL Server\90\COM\tablediff.exe" -sourceserver MyServer1 
                                                             -sourcedatabase MyDatabase1 
                                                             -sourcetable MyTable1 
                                                             -destinationserver MyServer1  
                                                             -destinationdatabase MyDatabase1 
                                                             -destinationtable MyTable2 
                                                             -et DiffsTable

This compares 2 tables in the same database on the same server and creates a new table called DiffsTable that holds the differences and

creates a T-SQL script file at d:\MyTable1_MyTable2_diff.sql

that holds the UPDATE/INSERT/DELETE statements to synchronize the 2 tables:

"C:\Program Files\Microsoft SQL Server\90\COM\tablediff.exe" -sourceserver MyServer1  
                                                             -sourcedatabase MyDatabase1 
                                                             -sourcetable MyTable1 
                                                             -destinationserver MyServer1  
                                                             -destinationdatabase MyDatabase1 
                                                             -destinationtable MyTable2 
                                                             -et DiffsTable 
                                                             -f d:\MyTable1_MyTable2_diff.sql

More info on this VERY COOL little tool in BOL here.

UPDATE: I've created a GUI for this tool. Look here.