digsby

5. digsby-The youngest application by far to make
the Hive Five, Digsby has taken the world by storm since we first mentioned it in February. Boasting integration with all of your IM networks as well as your email
and social networking (Facebook and
MySpace included), Digsby is converting
new users left and right with their simple
but appealing formula: IM + Email + Social
Networking = Digsby. Currently a Windows only app, Digsby's developers
promise that Mac and Linux versions are
in the oven—and that they're constantly squashing bugs from the still-young
Windows version.

http://www.digsby.com/

Whatsapp For PC for sure is the best app ever created for instant messaging. There is simply no reason why one won't wanna get it on their phone. 

Palringo

4. Palringo-Palringo is a free Rich Messaging Service
where you can express yourself in an
instant - using any combination of typed,
voice or picture messages you like, all
using your phone's data allowance. Palringo allows you to chat with your
friends and family who are on Windows
Live Messenger, Google Talk, AIM, ICQ,
Yahoo, Gadu Gadu, Jabber, and iChat on
your mobile phone or computer.
I personally prefer this as it provides Voice chat even in facebook!!
Download it from-
http://www.palringo.com/

Skype

3. Skype-There is a very popular IM called Skype.I’m sure you would have already used Skype. Skype is software
that enables the world’s conversations. Millions of individuals and businesses use
Skype to make free video and voice calls,
send instant messages and share files
with other Skype users. Every day,
people everywhere also use Skype to
make low-cost calls to landlines and mobiles. Skype also gives you chance for
shopping and business online.
It enables you to do video chat in high defination.
Get now from-
http://www.skype.com/

2. Meebo - Meebo lets users gather their friends on a single buddy list where
they can communicate in real-time across
different IM platforms, communities, and
traditional social networks. Users can
keep in touch with friends across dozens
of IM platforms, including AIM, Yahoo!, MSN, Google Talk, MySpace IM,
Facebook Chat, and more. eBuddy and
Meebo are two major sites to access
Instant messenger even if IM is blocked
for your server.
Get it now from
http://www.meebo.com/

eBuddy

1. eBuddy – You will just fall in love with eBuddy once you are in. This is the most
powerful and popular IM client for cell phones. eBuddy created the world’s first, independent, web browser-based instant
messaging service as e-Messenger in
2003. This web based messenger
enables you to chat with your MSN,
Yahoo, Google Talk, MySpace, Facebook,
ICQ and AIM buddies. This carry many simple yet interesting features and there
is no downloads, no installation or no
registration required.
Get from here
http://www.ebuddy.com/