For friends on a different EQ2 Server:
/tell server.character message
Current EQ2 Servers:
Antonia Bayle Lucan Dlere
Befallen Mistmoore
Blackburrow Najena
Butcherblock Nektulos
Crushbone Oasis
Everfrost Oggok
Guk Permafrost
Highkeep Runnyeye
Innothule Steamfont
Kithicor Unrest
Lavastorm

For friends playing Star Wars Galaxies:
/tell swg.server.character message
Current SWG Servers:
Ahazi Lowca
Bloodfin Naritus
Bria Radiant
Chilastra Scylla
Chimaera Shadowfire
Corbantis Starsider
Eclipse Sunrunner
FarStar Tarquinas
Flurry Tempest
Gorath Valcyn
Intrepid Wanderhome
Kauri Kettemoor

To send a message to a character in EverQuest:
/tell eq.server.character message
Everquest Servers:
Antonius Bayle = antonius Karana = karana
Ayonae Ro = ayonae Lanys T`Vyl = lanys
Bertoxxulous = bertox Luclin = luclin
Brell Serilis = brell Maelin Starpyre = maelin
Bristlebane = bristle Mithaniel Marr = mithaniel
Cazic Thule = cazic Morden Rasp = morden
Drinal = drinal Morell Thule = morell
Druzzil Ro = druzzil Povar = povar
E`Ci = eci Prexus = prexus
Erollisi Marr = erollisi Quellious = quellious
Fennin Ro = fenninro Rallos Zek = rallos
Firiona Vie = firiona Rodcet Nife = rodcet
Innoruuk = innoruuk Kane Bayle = kane
Saryrn = saryrn The Seventh Hammer = seventh
Sebilis = sebilis The Rathe = rathe
Solusek Ro = solusek The Tribunal = tribunal
Storms = storms Tholuxe Paells = tholuxe
Stromm= stromm Torvonnilous = torvon
Sullon Zek = sullon Tunare = tunare
Tallon Zek = talon Vallon Zek = vallon
Tarew Marr = tarew Vazaelle = vazaelle
Terris Thule = terries Veeshan = veeshan
The Nameless = nameless Xegony = xegony
Xev = xev Zebuxoruk = zebuxoruk