Found a really usefull site with a huge database of internet ports.

Also has a cool dns interface:

robin@trillian robin $ nslookup -q=txt 80.tcp.portsdb.org
Server:  junction.internal.image-data.com
Address:  192.168.1.102

Non-authoritative answer:
80.tcp.portsdb.org      text = "http"
80.tcp.portsdb.org      text = "Nimda"
80.tcp.portsdb.org      text = "www-http"
80.tcp.portsdb.org      text = "www"
robin@trillian robin $

Thanks to toby for the dig alternative:

robin@trillian robin $ dig -t txt 80.tcp.portsdb.org

; <> DiG 8.3 <> -t 80.tcp.portsdb.org
;; res options: init recurs defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0
;; QUERY SECTION:
;;      80.tcp.portsdb.org, type = TXT, class = IN

;; ANSWER SECTION:
80.tcp.portsdb.org.     3h54m53s IN TXT  "http"
80.tcp.portsdb.org.     3h54m53s IN TXT  "Nimda"
80.tcp.portsdb.org.     3h54m53s IN TXT  "www-http"
80.tcp.portsdb.org.     3h54m53s IN TXT  "www"

;; Total query time: 117 msec
;; FROM: trillian to SERVER: default -- 192.168.1.102
;; WHEN: Mon Jul  7 11:43:43 2003
;; MSG SIZE  sent: 36  rcvd: 108

robin@trillian robin $