Internet Relay Chat bots

Eggdrop
Eggdrop is a popular IRC bot and is the oldest IRC bot still in active development.

Infobot
Infobot is a Perl IRC bot, first written in 1995 by Kevin Lenzo.

Internet Relay Chat bot
An IRC bot is a set of scripts or an independent program that connects to Internet Relay Chat as a client, and so appears to other IRC users as another user.