Basic Commands

/tell (alias '/t') - Send a player a private message. You can scroll through all the people that whispered you recently by typing on the tab key.
/w - Send a player a private message. You can scroll through all the people that whispered you recently by typing on the tab key.
/chathelp (alias '/chat') - List of chat commands
/em (alias '/me') - Creates an emote
/exit - Quit the game
/follow (alias '/f') - Target a player and type this. You will follow that player.
/ghelp - For a list of guild commands
/invite (alias '/inv') - Invite a player to your party.
/logout - Log out of the game
/page - Pops up a large text message to alert the recipient
/party (alias '/p') - Sends a message to party chat
/played - Reports the amount of time you've played the game with that character.
/pvp - Enable your character to be attacked by other players in Player vs. Player combat.
/random [Y]: Generates a random number between X and Y, if Y isn't specified, then it will generate a number between 1 and X. This is very useful to determine who's going to have the right to loot a chest or harvest a resource.
/r - Reply to the last tell/private message. You can scroll through all the people that whispered you recently by typing on the tab key.
/say (alias '/s') - Send a message to people near you
/sit - When standing, your character will sit. Your character regains health more quickly when sitting.
/stand - When sitting, your character will stand.
/who - Lists the players online.
/yell (alias '/y') - Yells a message to the area around. Many players consider this to be "spam" so use it sparingly.
 

/cast allows you to cast spells by name. Type /cast (spell subtext) - Example: "/cast Fireball (Rank 1)". To add spell casting to a macro you can type it manually or shift-click a spell in your spell book to add the proper /cast line to the macro.

Chat Commands

/#, /c, /csay - Send text to channel # (e.g. /1 Hi!)
/announcements, /ann - Toggle join/leave announcements on a channel
/afk, /dnd - Set your Away From Keyboard or Do Not Disturb flags
/ban, /unban - Ban/unban a player from a channel
/chatlist, /chatwho, /chatinfo [channel] - List channels, or channel members
/cinvite, /chatinvite - Invite a player to a channel
/join, /channel, /chan - Join a channel
/kick - Kick a player off a channel
/leave, /chatleave, /chatexit [channel] - Leave a channel (or all channels)
/mod, /moderator, /unmod, /unmoderator - Change a player's moderator status
/moderate - Toggle moderation on a channel
/mute, /squelch, /unvoice, /unmute, /unsquelch, /voice - Change a player's permission
/password, /pass - Change password
 

/ginfo - Gives basic information about your guild
/g - Sends a chat message to all members of your guild
/o - Sends a chat message to all officers of your guild
/ginvite - Invites another player to join your guild
/gremove - Removes a player from your guild
/gpromote - Promotes a player one rank within your guild
/gdemote - Demotes a player one rank within your guild
/gmotd - Sets the guild's message of the day
/gquit - Removes you from your guild
/groster - Gives an entire guild roster (officers and leaders only)
/gleader - Sets another player as the guild leader (guild leader only)
/gdisband - Disbands your guild (guild leader only)
 

Voice (Sounds)
The following will play a sound! There are two to three variations for each one. The voices will be different depending on your character.

/inc - Incoming. You type this to warn your party that a monster is coming to attack
/charge
/flee
/assist
/oom - Out of mana, low on mana
/fol - Follow Me
/wait
/heal
/flirt
/follow
/goodbye
/grats
/hello
/help
/cheer
/fire
/incoming
/no
/silly
/thankyou
/welcome
/yes
/rasp - Sticking your tongue out sounds