AltSlashdot has an IRC Channel at ##altslashdot on chat.freenode.net. If you do not have an IRC client installed on your machine, you can use Freenode's webchat.
Registering a nickname
It is strongly recommended that new users register their nickname with NickServ so that others can not use it. To do this you can use the following command:
/msg NickServ REGISTER <password> <email-address>
After running this command you will receive an Email with instructions on how to confirm it is valid. If you are using an IRC client (not webchat) and you would like to have your IP Address/Hostname hidden from other users, you can go into the #freenode channel and ask about an unaffiliated cloak once you are logged into your NickServ account. A Freenode staff member should be able to help you out.