Important Dates in Bot History:

GT Bot - 199x - Author: Lance? - Note: The first mIRC based Bot?
GT Bot Sev2- 199x - Author: Lance? - Note: The first mass spreading bot via NetBios Passwords.
TKBot - 199x - Author: Thr34t-Krew - Note: IIS4 Unicode spreading Bot.
Kaiten - 2001? - Author: Contem - Note: The first *nix Bot?
SDBot - 2002 - Author: [sd] - Note: The 'mother' of all IRC Bots, and the base for most today.
D3ADLiN3.8k.com - 14/05/2003 - Author: Me! - Note: Date my first Bot website started! Oldest Bot related website on the Web which is still up and running!
SDBot with Syn Flood - 200x - Author: [sd] & Tesla - Note: First public Bot with SYN flood.
SpyBot - 200x - Author: Mike - Note: First public advanced mod of SDBot.
rBot - 200x- Author: Nils - Note: First public NTPass C++ Bot based on SDBot.
MSBlaster - 200x Author: ? - Note: Not strictly a Bot but it changed the Internet for ever.
rxBot - 200x - Author: Nils/RacerX - Note: More advanced version of rBot, first in the series of RAT type bots.
AgoBot - 200x - Author: Ago - Note:
PhatBot - 200x - Author: Ago/Phatty - Note:
WonkBot - 200x - Author: Ago/Phatty/Wonk Note:
Storm Worm - 2008? - Author: ? - Note:
Hydra - 2008 - Author: Ahmed Ramzy? - Note: Infects DLink Routers; First Bot to infect physical devices.
Conficker - 2009 - Author: ? - Note: Biggest recorded BotNet, estimated 8.9 million (ref).

I'll update this as I get more info.