You can use Pidgin for Yahoo Messenger. You need to create you account in Pidgin, and then when adding buddies, add the name only and do not add @yahoo.com etc. Also, make sure that in the combo box that appears you choose your Yahoo account and not the other Accounts you have set up in Pidgin. You can also use Pidgin for Rediff messenger. You have to download the source code, compile and then restart your Pidgin messenger in Linux.