Status of membership and implementation
As of 21 December 2007, 24 states and Monaco (treated as part of France) had abolished border controls on persons among themselves, an increase from 15 on 20 December 2007. The nine new countries which entered the Schengen travel area in 2007 were: the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia.[75] These states all entered the EU three years previously. Switzerland entered the Schengen area on 12 December 2008. Any non-Schengen traveller having a valid Schengen visa has been allowed to travel throughout these 25 countries from their accession. They were required to upgrade their border checks with non-Schengen states before border controls would be dropped with them.
Cyprus, which entered the EU alongside these other states, did not meet the criteria and thus has requested a delay for a year, while Romania and Bulgaria, which joined the EU in 2007, are still bringing their border controls up to the required standard.
http://en.wikipedia.org/wiki/Schengen_Agreement