Looking Glass servers are computers on the Internet running one of a variety of publicly available Looking Glass software implementations. A Looking Glass server (or lg server) is accessed remotely for the purpose of viewing routing info. Essentially, the server acts as a limited, read-only portal to routers of whatever organization is running the lg server. Typically, publicly accessible looking glass servers are run by Internet service providers (ISPs) or NOCs.
Level3:
http://lg.level3.net/
Telia
http://looking-glass.telia.net/
nLayer
http://lg.nlayer.net/
Highwinds
http://lookingglass.hwng.net/
One of the most complete all-in-one list of looking glass resources of different providers:
http://www.bgp4.as/looking-glasses
One more list of looking glass resources:
http://www.lookinglass.org/
