Have you even used Skype™ for Linux? That IM with awful one-window-per-chat GUI? Do you know how it feels to find a neede window in your taskbar/dock/Unity launcher/whatever you have?
Here comes... SkypeTab. See the video, it's self-describing.
Installation for Ubuntu:
sudo add-apt-repository ppa:keks9n/skypetab
sudo apt-get update
sudo apt-get install skypetab-ng
For Debian Squeeze you can use ppa for Ubuntu Lucid (add "deb http://ppa.launchpad.net/keks9n/skypetab/ubuntu lucid main" to your sources.list and import repository key using "apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 41A6E3C3"), it seems to be compatible.
If it crashes when you try to open new tab, just go to Skype's settings and select any other GUI theme than "GTK+" and "Desktop settings"