Yakuake (Yet Another Kuake KDE terminal emulator) is a KDE console application that I use the most for months now. Before, I used to use konsole but after installing yakuake, I rarely use konsole anymore. The most important feature is the quick easy access to it by pressing a key. The key is configurable. I can't remember what is the default key for it but I choose F8 because the default is used by another application.
Debian - use synaptic or aptitude or apt-get install yakuake
Mandriva - use graphical rpmdrake or urpmi yakuake
other distros - please consult your distro documentation.
I have read a Linux mag (don't know which) that it is favorite among KDE developers and will be replacing konsole. I don't know whether this is true. Anyone can confirm this?
Yakuake home page (new update)
Yakuake - An easy access konsole for KDE
More info : http://www.kde-apps.org/content/show.php?content=29153