I'm using imo to message my friends on all of my accounts, MSN, Facebook, Skype, Yahoo, Google Talk, AIM and others.
imo also lets you quickly send voice ims, create group chats, and share photos.
It's free and easy to use.
Web: https://imo.im
iPhone: http://itunes.apple.com/us/app/imo-instant-messenger/id336435697
iPad: http://itunes.apple.com/us/app/imo-instant-messenger-for/id405179691
Android: https://market.android.com/details?id=com.imo.android.imoim
