Instant Messaging (IM) clients for Linux
Linux has excellent support for all the major Instant Messaging protocols. Infact some of the IM clients are versatile and support multiple protocols in an integrated user interface. If you are looking for information specifically about IRC then please check out the MiniIRCGuide
Pidgin (previously know as Gaim) is undoubtedly the most popular free and open source IM client available. It supports a lot of IM protocols like : Msn, Yahoo, Aim, IRC, Jabber etc : http://www.pidgin.im However it lacks webcam / video chat support.
Amsn : http://www.amsn-project.net calls itself the free open source MSN messenger clone and doesn't lie because it comes packed with an impressive list of features
Kopete : KDE Instant Messenger like Pidgin supports multiple IM protocols : http://kopete.kde.org/
Console based IM Clients
There are command line alternatives too for Instant Messaging.
naim is a console client for AIM,ICQ, IRC, Lily CMC : http://naim.n.ml.org/about
Chatting in Nepali
Check the UbuntuNepali page on how type in Nepali which should work with most GUI based IM clients.