I like man pages.
So today I wrote a little script called kdedoxyman.sh that uses doxygen to generate API Dox in man page format
Replacing "/path/to/kde" in these instructions with the real path to your KDE4 installation.
Repeat for other KDE modules: kdepimlibs, etc.
Now add /path/to/kde/share/man to your MANPATH environment variable (or add "MANPATH /path/to/kde/share/man" to your /etc/man.config file).
At this point you should be about to run 'man KAboutData', for example, from the comfort of your konsole command line.
Of course, api.kde.org is useful too :)