Estas son las búsquedas que tengo programadas en Opera, donde «%s» es la cadena que ingreso en la barra de direcciones. Las que más uso son «drae», «whois», «rfc» e «ipcalc».

(drae) Diccionario de la Real Academia Española:
GET http://buscon.rae.es/draeI/SrvltGUIBusUsual?TIPO_BUS=3&LEMA=%s

(gl) Google Luck
GET http://www.google.com/search?q=%s&num=%i&btnI

(rfc) Internet RFC Archives
GET http://www.faqs.org/rfcs/rfc%s.html

(bcp) Internet BCP Archives
GET http://www.faqs.org/rfcs/bcp/bcp%s.html

(whois) WHOIS @ Samspade.org
POST http://samspade.org/whois
Cadena de búsqueda: query=%s&server=auto

(en_es) English to Spanish — WordReference.com
GET http://www.wordreference.com/es/translation.asp?tranword=%s

(es_en) Name=Spanish to English — WordReference.com
GET http://www.wordreference.com/es/en/translation.asp?spen=%s

(pt_es) Name=Portuguese to Spanish — WordReference.com
GET http://www.wordreference.com/ptes/%s

(es_pt) Name=Spanish to Portuguese — WordReference.com
http://www.wordreference.com/espt/%s

(mac) Name=Vendor/Ethernet MAC Address Lookup
GET http://www.coffer.com/mac_find/?string=%s

(ipaclc) Name=Subnet Calculator
POST http://share-foo.com/SubnetCalc.php
Cadena de búsqueda: my_net_info=%s&subnetcalc=Calculate

(define) Google Definitions
GET http://www.google.com/search?q=define:%s

(lyr) Name=Leo’s Lyrics via Google Luck
GET http://www.google.com/search?q=site:leoslyrics.com+%s&btnI

Aquí están las mismas búsquedas pero en formato .INI, para su pegado en ~/.opera/search.ini. Sólo se debe tener cuidado con que los nombres de sección y los campos ID no choquen con otras consultas.

[Search Engine 6]
ID=1000005
Name=Diccionario de la Real Academia Española
Verbtext=0
URL=http://buscon.rae.es/draeI/SrvltGUIBusUsual?TIPO_BUS=3&LEMA=%s
Query=
Key=drae
Is post=0
Has endseparator=0
Encoding=iso-8859-1
Search Type=0
Position=-1
Nameid=0
Deleted=0

[Search Engine 7]
ID=1000006
Name=Google Luck
Verbtext=0
URL=http://www.google.com/search?q=%s&num=%i&btnI
Query=
Key=gl
Is post=0
Has endseparator=0
Encoding=iso-8859-1
Search Type=0
Position=-1
Nameid=0
Deleted=0

[Search Engine 8]
ID=1000007
Name=Internet RFC Archives
Verbtext=0
URL=http://www.faqs.org/rfcs/rfc%s.html
Query=
Key=rfc
Is post=0
Has endseparator=0
Encoding=iso-8859-1
Search Type=0
Position=-1
Nameid=0
Deleted=0

[Search Engine 9]
ID=1000008
Name=Internet BCP Archives
Verbtext=0
URL=http://www.faqs.org/rfcs/bcp/bcp%s.html
Query=
Key=bcp
Is post=0
Has endseparator=0
Encoding=iso-8859-1
Search Type=0
Position=-1
Nameid=0
Deleted=0

[Search Engine 10]
ID=1000009
Name=WHOIS @ Samspade.org
Verbtext=0
URL=http://samspade.org/whois
Query=query=%s&server=auto
Key=whois
Is post=1
Has endseparator=0
Encoding=iso-8859-1
Search Type=0
Position=-1
Nameid=0
Deleted=0

[Search Engine 11]
ID=1000010
Name=English to Spanish -- WordReference.com
Verbtext=0
URL=http://www.wordreference.com/es/translation.asp?tranword=%s
Query=
Key=en_es
Is post=0
Has endseparator=0
Encoding=utf-8
Search Type=0
Position=-1
Nameid=0
Deleted=0

[Search Engine 12]
ID=1000011
Name=Spanish to English -- WordReference.com
Verbtext=0
URL=http://www.wordreference.com/es/en/translation.asp?spen=%s
Query=
Key=es_en
Is post=0
Has endseparator=0
Encoding=utf-8
Search Type=0
Position=-1
Nameid=0
Deleted=0

[Search Engine 13]
ID=1000012
Name=Portuguese to Spanish -- WordReference.com
Verbtext=0
URL=http://www.wordreference.com/ptes/%s
Query=
Key=pt_es
Is post=0
Has endseparator=0
Encoding=utf-8
Search Type=0
Position=-1
Nameid=0
Deleted=0

[Search Engine 14]
ID=1000013
Name=Spanish to Portuguese -- WordReference.com
Verbtext=0
URL=http://www.wordreference.com/espt/%s
Query=
Key=es_pt
Is post=0
Has endseparator=0
Encoding=utf-8
Search Type=0
Position=-1
Nameid=0
Deleted=0

[Search Engine 15]
ID=1000014
Name=Vendor/Ethernet MAC Address Lookup
Verbtext=0
URL=http://www.coffer.com/mac_find/?string=%s
Query=
Key=mac
Is post=0
Has endseparator=0
Encoding=utf-8
Search Type=0
Position=-1
Nameid=0
Deleted=0

[Search Engine 16]
ID=1000015
Name=Subnet Calculator
Verbtext=0
URL=http://share-foo.com/SubnetCalc.php
Query=my_net_info=%s&subnetcalc=Calculate
Key=ipcalc
Is post=1
Has endseparator=0
Encoding=utf-8
Search Type=0
Position=-1
Nameid=0
Deleted=0

[Search Engine 17]
ID=1000016
Name=Google Definitions
Verbtext=0
URL=http://www.google.com/search?q=define:%s
Query=
Key=define
Is post=0
Has endseparator=0
Encoding=utf-8
Search Type=0
Position=-1
Nameid=0
Deleted=0

[Search Engine 18]
ID=1000016
Name=Leo's Lyrics via Google Luck
Verbtext=0
URL=http://www.google.com/search?q=site:leoslyrics.com+%s&btnI
Query=
Key=lyr
Is post=0
Has endseparator=0
Encoding=utf-8
Search Type=0
Position=-1
Nameid=0
Deleted=0