This list of tag pairs that differ by pluralization. The number inside brackets was number of question tagged with that tags.

* [tag:services] (356)  [tag:service] (243)
* [tag:hosts] (179) [tag:host] (149)
* [tag:vhosts] (295)    [tag:vhost] (122)
* [tag:sockets] (178)   [tag:socket] (91)
* [tag:groups] (197)    [tag:group] (85)
* [tag:interfaces] (112)    [tag:interface] (84)
* [tag:connection] (477)    [tag:connections] (63)
* [tag:packages] (92)   [tag:package] (62)
* [tag:modules] (111)   [tag:module] (61)
* [tag:image] (161) [tag:images] (60)
* [tag:headers] (82)    [tag:header] (56)
* [tag:browsers] (79)   [tag:browser] (56)
* [tag:domain] (1638)   [tag:domains] (53)
* [tag:backup] (2924)   [tag:backups] (50)
* [tag:parallels] (54)  [tag:parallel] (49)
* [tag:command] (85)    [tag:commands] (44)
* [tag:share] (130) [tag:shares] (43)
* [tag:zone] (96)   [tag:zones] (36)
* [tag:cables] (82) [tag:cable] (33)
* [tag:template] (34)   [tag:templates] (32)
* [tag:index] (73)  [tag:indexes] (31)
* [tag:application] (80)    [tag:applications] (29)
* [tag:notification] (88)   [tag:notifications] (28)
* [tag:packet] (68) [tag:packets] (28)
* [tag:partition] (629) [tag:partitions] (26)
* [tag:alias] (215) [tag:aliases] (25)
* [tag:protocol] (31)   [tag:protocols] (25)
* [tag:cookies] (71)    [tag:cookie] (24)
* [tag:request] (69)    [tag:requests] (22)
* [tag:plugin] (45) [tag:plugins] (21)
* [tag:record] (27) [tag:records] (21)
* [tag:web-services] (82)   [tag:webservice] (18)  [tag:webservices] (30) 
* [tag:serial-ports] (65)   [tag:serial-port] (18)
* [tag:volume] (46) [tag:volumes] (18)
* [tag:drive] (59)  [tag:drives] (16)
* [tag:route] (316) [tag:routes] (15)
* [tag:path] (163)  [tag:paths] (15)
* [tag:alerts] (98) [tag:alert] (15)
* [tag:jail] (65)   [tag:jails] (15)
* [tag:netflow] (23)    [tag:netflows] (13)
* [tag:font] (20)   [tag:fonts] (13)
* [tag:blade] (62)  [tag:blades] (12)
* [tag:graph] (45)  [tag:graphs] (12)
* [tag:table] (43)  [tag:tables] (12)
* [tag:instance] (33)   [tag:instances] (12)
* [tag:transactions] (23)   [tag:transaction] (12)
* [tag:disk] (552)  [tag:disks] (11)
* [tag:application-pools] (169) [tag:application-pool] (11)
* [tag:wildcard] (143)  [tag:wildcards] (11)
* [tag:servlet] (29)    [tag:servlets] (11)
* [tag:file-server] (161)   [tag:fileservers] (10)
* [tag:credentials] (78)    [tag:credential] (10)
* [tag:device] (52) [tag:devices] (10)
* [tag:attachment] (47) [tag:attachments] (10)
* [tag:restrictions] (30)   [tag:restriction] (10)
* [tag:mailing-list] (42)   [tag:mailing-lists] (9)
* [tag:task] (28)   [tag:tasks] (9)
* [tag:locale] (62) [tag:locales] (8)
* [tag:sysctl] (49) [tag:sysctls] (8)
* [tag:parameters] (41) [tag:parameter] (8)
* [tag:tutorial] (20)   [tag:tutorials] (8)
* [tag:providers] (14)  [tag:provider] (8)
* [tag:stats] (15)  [tag:stat] (7)
* [tag:cluster] (924)   [tag:clusters] (6)
* [tag:login] (595) [tag:logins] (6)
* [tag:language] (30)   [tag:languages] (6)
* [tag:startup-scripts] (69)    [tag:startupscript] (5)
* [tag:communication] (30)  [tag:communications] (5)
* [tag:web-applications] (230)  [tag:webapplication] (4)
* [tag:administrator] (192) [tag:administrators] (4)
* [tag:interrupts] (37) [tag:interrupt] (4)
* [tag:virus] (107) [tag:viruses] (3)

##Exception

###Keep both tags

* [tag:http] (1266) [tag:https] (1060) <--- different protocol
* [tag:local] (100) [tag:locale] (8) <--- different term(?) 
* [tag:guid] (9)    [tag:guides] (7) <--- different term(?) 
* [tag:smtp] (1712) [tag:smtps] (3) <--- different protocol

###Burn both tags

* [tag:mysites] (6) [tag:mysite] (4)

###Already cleanup

* [tag:loop] (48)   [tag:loops] (5)