Pidgin, best ever all-in-one messenger. Best, because it has a lot of plugins. If you have multiple GMail accounts, such as personal GMail, and your workplace uses Google App, then you can just use Pidgin. Need not open so many applications.
If you need Skype, for messeging only or group chat, install skype4pidgin plugin. It is better to use it instead of running heavy Skype for Linux Alpha or very old version of Skype. Using outlook.com web version Skype cannot give any notification, but allows you to view the images directly. But still, using Google Talk/Hangout and Skype services together through Pidgin is much more convenient.
I tried with Telegram also. It works. There are various plugins available. If you need notifications from multiple chat services (including Facebook), Pidgin is the best!