Object Identifiers (OIDs) are unique identifying codes allocated in a hierarchical manner. There are currently millions. The entire Internet has an OID of 1.3.6.1; all Internet resources with OIDs are subsidiary to this. The IETF's RFC 3001 (http://www.ietf.org/rfc/rfc3001.txt) proposed a "urn:" namespace for OIDs, which has yet to be implemented.

Registries of known OIDs:
* http://www.alvestrand.no/objectid/ 
* http://asn1.elibel.tm.fr/en/oid/

See also: http://asn1.elibel.tm.fr/en/oid/standards.htm (OID registration standards)

''I tried visiting the above, and my employer's NetNanny blocked the site, claiming that it was a pr0n site.  Could someone not behind a firewall confirm the URL?  (The NetNanny service which the employer subscribes to is notorious for blocking non-offensive sites).

Compare and contrast: GloballyUniqueIdentifier

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ObjectIndentifiers are commonly associated with SimpleNetworkManagementProtocol (SNMP).  Are they used outside the scope of SNMP?