At this time, I would give you some of Chat Client software that developed to use in IRC and work with iPhone and iPod Touch. To simplify that term, we can called as IRC Client for iPhone or just IRC Chat Client for iPod Touch.
Commercial IRC Client for iPhone
If you looking for IRC Client for iPhone that available in iPhone iTunes AppStore, you can try Colloquy for iPhone and iPod Touch. It’s has many features such as supports IRC command, Nickname and Emoticons, Provide User Information (whois), search able room member list and many more.
Download Colloquy at iPhone AppStore
Advance information about this commercial (that means you must buy it to use it) you can find at official site of Colloquy at colloquy.mobi
Free IRC Client for iPhone
If you want a free IRC Client for your iPhone you can use one of this list below:
IRCm – IRC on your iPhone
IRCm is Free IRC Client for iPhone under GNU Lesser General Public License. Not much features that I found in this client, just try by your self to find out more about IRCm. iRCm build in GUI base Internet Relay Chat Mobile for Apple iPhone (the tag line of iRCm)
Free Web Base IRC Client
Another alternative for you if you want to chat in IRC using your iPhone is using web base IRC Client. One of the solution of this is using mibbit. Just pointed your iphone browser (safari) to www.mibbit.com and then you can make nickname and start chatting in IRC from there. No need to download, no need to install, all you have to do just open web browser and type the url of mibbit.
Features in mibbit we irc client: connect to multiple servers, auto connect and join favourite, nickname, smiley / emoticons, private message and more.