however, there are still certain areas in the united states in which the older pay phones still run on the older frequencies, so it is still possible to use an old blue box in those areas, I have yet to find them because they are being kept secret so they can still be used by a select few for a little while longer.
This would be called phreaking.
I know there are TONS of sites out there that tell you how to phreak and stuff....
not sure but there might be a link off of www.astalavista.com or something....
Also... I'd like to add that phone phreaking, and possession of a blue box, or any other box including, red, black, cyan, and cardboard (heh, j/k on the last) are considered illegal, even though they no longer work, it is still considered contraband and can carry a fine, and possibly jail time, I myself still wish to build one, but only for display, mounted in a lexon case.