From http://www.kubuntu.org/news/kde-4.1:
KDE 4.1 has been released and packages are available for Kubuntu 8.04, the Hardy Heron. These packages install to /usr/lib/kde4 and can be installed along side your existing KDE 3 installation.
Instructions
The updated packages for Kubuntu 8.04 are located in the Kubuntu Member’s KDE 4 Personal Package Archive (PPA) repositories. To update to the release candidate of KDE 4.1, please follow these instructions:
1. Add deb http://ppa.launchpad.net/kubuntu-members-kde4/ubuntu hardy main to your /etc/apt/sources.list.
2. If you already have the kubuntu-kde4-desktop packages installed, simply type sudo apt-get update && sudo apt-get dist-upgrade and answer the questions in which you are prompted. If you do not have kubuntu-kde4-desktop installed, simply type sudo apt-get update && sudo apt-get install kubuntu-kde4-desktop and answer the questions. Both of these options are to be typed at the command prompt.kdeplasma-addons contains new Plasma fun.
Thanks to Harald, Guillaume, Steve, Jon and Arby for preparing these packages.
