A calculator supporting addition, substraction, multiplication and division (respectively : ADD, SUB ,MUL, and DIV operations). More information here.

dig 2.8.add.calc.postel.org @dns.postel.org +short
dig 8.2.sub.calc.postel.org @dns.postel.org +short
dig 2.8.mul.calc.postel.org @dns.postel.org +short
dig 8.2.div.calc.postel.org @dns.postel.org +short

IP to ASN Mapping

A service providing a way to map IPv4 and IPv6 addresses or prefixs to ASNs, get information about ASNs, and even find possible peers. More details here.

Mapping an IP address or prefix to a corresponding BGP Origin ASN:

dig TXT +short
"15169 | | US | arin |"
dig 4.8.8.origin.asn.cymru.com TXT +short
"15169 | | US | arin |"
dig TXT +short
"15169 | 2001:4860::/32 | US | arin | 2005-03-14"

Getting information about a given ASN:

dig AS15169.asn.cymru.com TXT +short
"15169 | US | arin | 2000-03-30 | GOOGLE - Google Inc.,US"


dig any google-public-dns-a.google.com +noall +answer
; <<>> DiG 9.8.3-P1 <<>> any google-public-dns-a.google.com +noall +answer
;; global options: +cmd
google-public-dns-a.google.com.	38271 IN TXT	"http://xkcd.com/1361/"
google-public-dns-a.google.com.	38271 IN AAAA	2001:4860:4860::8888
google-public-dns-a.google.com.	38271 IN A

more stuff at http://www.cambus.net/interesting-dns-hacks/