For unknown reason Debian maintainers don't support kismet software in official repositories. As result, Debian and all Debian-derived Linux distributive contain outdated version of kismet (stable version is 2011-03-R2, as for Debian it is only 2008-05-R1).
It's easy to update it in your distro, Ubuntu x86/x86-64 users can use pre-compiled official repos from Kismetwireless team:
For Ubuntu Maverick (10.x): deb http://www.kismetwireless.net/code/ maverick kismet
For Ubuntu Natty (11.x): deb http://www.kismetwireless.net/code/ natty kismet
For Ubuntu Precise (12.x): deb http://www.kismetwireless.net/code/ precise kismet
To add the Kismet signing key (signed by my primary key, available above) to your trusted keys:
curl https://www.kismetwireless.net/code/dists/kismet-release.gpg | sudo apt-key add -
For Raspbian users I've built kismet_2011-03-R2-1ubuntu1_armhf.deb. Just download and install it.
P.$.: kismet_2011-03-R2-1ubuntu1.diff.gz is also available.