One of my favorite softwares which I use almost every second of the day when I’m online. Pidgin is a  all-in-one IM client that resembles AIM. Pidgin works with AIM, Bonjour, Gadu-Gadu, Google Talk, Groupwise, ICQ, IRC, MSN, MySpaceIM, QQ, SILC, SIMPLE, Sametime, XMPP, Yahoo! and Zephyr all at once

Latest Changes made are

• In the Join/Part plugin, add the ability to apply the rules to buddies. By default, joins and parts for buddies are still shown
• Support SOCKS proxies specified in GNOME or Windows proxy settings
• Fix some possible crashes in MSNP15
• Enable a default SSL trust relationship for MSN servers
• Avoid disconnecting from XMPP servers on parse errors that are non-fatal
• Include some perl files that were mistakenly omitted in 2.5.0
• Prevent use of custom smilies without “shortcuts.”
• Fix a crash that could appear with AIM buddy tooltips
• General refresh of many icons in the interface
• Many cleanups to artwork source are now included in the distribution
• A new “throbber” animation has been added to indicate when accounts are connecting

This is stable, configurable and reliable. The folks who worked on  it put a lot into it and the interface is simple and very easy to use.

Download : Pidgin for Windows 2.5.1