Seems like I've got something to do tonight at home: <a href="http://dot.kde.org/1133270759/">KDE 3.5 Released</a> Currently, I'm using version 3.4.3 in the (K)ubuntu Breezy version. There's a separate <a href="http://kubuntu.org/announcements/kde-35.php">KDE 3.5 repository for Ubuntu users</a>:
<blockquote>deb http://kubuntu.org/packages/kde35 breezy main</blockquote>
Just add it to /etc/apt/sources.list, update and upgrade.
By the way, the KDE web site has a <a href="http://www.kde.org/announcements/visualguide-3.5.php">visual guide</a> which explains some of the new features. It makes clear what's hot and new in KDE, in an easy way.