We went on a day trip to a place to the East of Montevideo; took a few hours to get there by bus.. Punta del Este, I think it is called? That was really nice – kind of a holiday retreat for the rich (and these days not so rich ;o)).
Other than that we tried to visit the Football Museum, but it was closed – so not sure if that is worth seeing? The park area around it was nice though :o)
Hope you have a great time :oD