The standard country template on the Wiki contains a field for internet top-level domain. I know this has been done in a rather ad-hoc fashion in the past but I thought it might be useful to have a central list of them, for reference purposes and to spot any potential conflicts. Below are all the countries in the game and their top level domain according to their wiki page. At the moment there are group of countries (all forum-based) that do not have a domain listed. I have highlighted these in red and encourage the controllers to assign them one that isn't already used.
Aldegar: .ag
Alduria: .al
Aloria: .alo
Badara: .bd
Baltusia: .bt
Barmenistan: .bar
Bazgaristan: none
Beiteynu: .bu
Beluzia: .bz
Bianjie: .bj
Cildania: .cd
Cobura: .cob
Dalibor: .db
Dankuk: .dr
Davostan: .dv
Deltaria: .dt
Dolgava: .dol
Dorvik: .dk
Dundorf: .dun
Egelion: .eg
Endralon: .ez
Gaduridos: .gd
Hanzen: .hz
Hobrazia: .hb
Hulstria and Gao-Soto: .gh
Hutori: .hut
Ikradon: .hwm
Istalia: .ist
Istapali: none
Jakania: .ck
Jelbania: .jel
Kafuristan: .kaf
Kalistan: .ks
Kalopia: .ka
Kanjor: .kj
Kazulia: .kz
Keymon: .ky
Kimlien: .kl
Kirlawa: .kw
Kizenia and New Endralon: .nek
Kundrati: .ku
Kurageri: .krg
Likatonia: .lk
Liore: .li
Lodamun: .lo
Lourenne: .lr
Luthori: .lu
Malivia: .mv
Medina: .mad
Midway: none
Mina: none
Mordusia: .mor
Narikaton and Darnussia: .nk
New Alduria: .na
New Englia: .nwe
New Verham: .nv
North Dovani: none
Noumonde: .nou
Ntoto: .to
Ostland: none
Pontesi: .pon
Rapa Pile: none
Rildanor: .ril
Rutania: .rt
Saridan: .sd
Seko: .sk
Selucia: .su
Solentia: .sol
Statrica: .st
Suyu Llaqta: .sl
Talmoria: .tl
Telamon: .tel
Temania: none
Trigunia: .tr
Tropica: .tpa
Tukarali: .tk
Utari Mosir: none
Utembo: .utm
Valruzia: .wr
Vanuku: .van
Vascania: .vk
Vorona: .va
Yingdala: .yi
Zardugal: .zrd