There aren't too many numbers station resources on the net, but here are the ones that I'm aware of.
Please let me know of any others.
Other sites of interest
The National Security Agency (NSA) has a web site available,
which includes information on the
VENONA project, which was the
program which suceeded in breaking many Soviet messages sent during and after WWII, related to
espionage here in the US. These decoded messages allowed the arrest and conviction of many of the
"Atomic Spies" including the Rosenbergs. Though the Soviets used one time pads, they made the
critical error in using them more than once.