A friend bugged me about the gnome clock applet that had evolution integration while the KDE clock applet doesn't have KOrganizer integration.
So I decided to hack something on it during the night...
The result can be seen here :

As you can see, days with an event have a blue circle for background... Ugly but enough with my graphic abilities. And when you click on a day in the calendar, korganizer opens itself on this day...
The patch is really simple and can be found here : http://www.pinaraf.info/clock_applet.patch
For the compilation, I tried to understand. Well, I hope I'm not too wrong in the explanations :
1- download kdebase-3.5.7 (may work with another kdebase... may not work... who knows...)
2- extract
3- go into the subfolder kicker/applets/clock and apply the patch (typ : patch -p1 < ~/clock_applet.patch for instance)
4- go back into the "root" of kdebase-3.5.7
5- launch ./configure
6- launch automake-1.9 (or if somebody still has hairs, he can look at this and explain how to do it the right way)
7- since you don't want to waste your CPU to compile the whole kdebase stuff compile with the following commands :
8- cd kicker/libkicker
9- make
10- cd ../applets/clock
11- make
12- make install as root.
Then you can relaunch kicker using the command dcop kicker Panel restart. Et voila...
You've got an ugly-looking integration between Korganizer and the clock applet, with a dependency on kdepim for a kdebase applet... Since kdepim is splitted with kdepimlibs, I hope it has already been done in KDE4... (I don't use korganizer so I didn't test this yet)
Any comment, feature request... can be written here. But don't expect every feature request to be accepted and worked on : I consider this as a waste of time...