See for basic commands.

These are more usefull advanced commands. Most people will never use many of these commands, but they are good to know at times. Some are limited to channel ops.

WHO Command
Searches User Information (-i users only) for supplied information.
Syntax: WHO <mask>
WHO <nickname>
WHO <#channel>

WHOWAS Command
Retrieves previous 'WHOIS' information for users no longer connected to the server.
Syntax: WHOWAS <nickname>

RULES Command
Reads the ircd.rules file and sends the contents to the user.
Syntax: RULES

LUSERS Command
Provides Local and Global user information.
Syntax: LUSERS

MAP Command
Provides a "Network Map" of the IRC network. Mainly used for routing purposes.
Syntax: MAP

STATS Command
Provides certain Statistical information about the server. See the flags addendum I will soon be writing.
Syntax: STATS <flags>

LINKS Command
Lists all of the servers currently linked to the network.
Syntax: LINKS

ADMIN Command
Provides Administrative information regarding the server.
Syntax: ADMIN <server>

TOPIC Command
Sets/Changes the topic of the channel in question, or just display the current Topic.
Syntax: TOPIC <channel>
TOPIC <channel> <topic>

INVITE Command
Sends a user an invitation to join a particular channel. Channel operator only.
Syntax: INVITE <user> <channel>

KICK Command
Removes a user from a channel. Can only be used by Operators or Half-Ops.
Syntax: KICK <channel> <user> <reason>

AWAY Command
Sets your online status to "Away".
Syntax: AWAY <reason> (Marks you as 'Away' with the reason given)
AWAY (Un-marks you as 'Away')

HELPOP Command
Get help on IRC commands.
Syntax: HELPOP

KNOCK Command
For channels which are invite only, you can "Knock" on the channel to request an invite.
Syntax: KNOCK <channel> <message>

MODE Command
Sets a mode on a Channel or User. See the flags addendum I will soon be writing.
Syntax: MODE <channel/user> <mode>

Ignores messages from a user or list of users at the Server itself.
Syntax: SILENCE +<nickname> (Adds a nickname to SILENCE list).
SILENCE -<nickname> (Removes a nickname from the SILENCE list).
SILENCE (Lists the current SILENCE list)

An alias to allow you to identify to NickServ or ChanServ with your password.
Syntax: IDENTIFY <password>