This one (pictured above) uses a book case to divide the table into half. I love how simple it looks when finished.
The plans are avavilable here at do it yourself. You can either buy a bookcase and modify it or build your own.
This one is a bit more expensive as it uses a plexiglass panel as a divider. I think I would just use a piece of wood and paint it, that way the kids couldn't see each other and we might get more work done ;)