The Museum of Communications
As described at String Can Phone:
The Museum of Communications is a no-frills homage to the history of conversing with others unhindered by distance. Located in Seattle, WA, the museum is a virtual warehouse of every communications device ever devised, including wired, indoors telephone poles. Of particular note is the display of six generations of fully-operational central office switch frames. We are so stirred upon seeing this collection that we are inspired to pick up our plastic, magically cordless telephone handset and ask the operator for Pennsylvania 6-5000.
dead link: http://www.museumofcommunications.org/