KDE 4.2 has been released. Jaunty (current development release) users can do a full upgrade to get the latest packages. Packages for 8.10 (Intrepid) are in intrepid-backports.
KDE 4.2 Release Candidate 1 has been released and packages are available for Kubuntu 9.04 "Jaunty". Packages for Kubuntu 8.10 "Intrepid" are compiling and will be available shortly, check back soon if they are not all available when you read this. Read more for details.
KDE 4.2 Beta 1 has been released and packages are available for Kubuntu 8.10, the Intrepid Ibex. Through unexpected hospital visits and endless waves of turkey & other merriments, the Kubuntu packaging ninjas always prevail. (Even if they are a week and a half late) These packages install to their normal locations and will upgrade your current KDE 4.1.x installation.