IM Protocol  

Creator  

Cspace

Cspace

Gadu-Gadu

Gadu-Gadu

Gale

Dan Egnor

IRC

Jarkko Oikarinen

MSNP (Windows Live Messenger, etc)

Microsoft

OSCAR protocol (AIM, ICQ)

AOL

PSYC (Protocol for SYnchronous Conferencing)

PSYC Project

Retroshare

Retroshare

RVP (Windows Messenger, etc)

Microsoft

SIP/SIMPLE

IETF

Skype Protocol

Skype

TOC protocol (deprecated)

AOL

TOC2 protocol

AOL

XMPP (Jabber)

Jeremie Miller, standardized via IETF

YMSG (Yahoo! Messenger)

Yahoo!

Zephyr Notification Service

?

IM service

Toatl User counts

AIM

100 million

eBuddy

35 million

Gadu-Gadu

6 million

Gizmo5

[1], mobile and PC

IBM Lotus Sametime

17 million

ICQ

15 million

IMVU

1 million

Mail.ru Agent

1 million daily

Meebo

1 million 

mundu messenger

> 2 million 

MXit

11 million 

Paltalk

3.3 million unique visitors per month

PSYC

1 million  (daily) 

Skype

309 million 

Tencent QQ

783 million 

VZOchat

>550,000

Windows Live Messenger

330 million 

Xfire

11.5 million 

XMPP

40-50 million 

Yahoo! Messenger

248 million