Qt is a toolkit for building a GUI for X in C++. 
There are some user documentation files in ${QT_DOC}, but
the main documentation is in the qt4-html package, 
or on the web (${HOMEPAGE}).

There is also a qt4-examples package, that contains tutorial, demos
simple example programs (source + binaries).

There's a debug version of the libraries: qt4-debug.

There are database plugins: qt4-mysql and qt4-postgresql.

People who want to use qt4 to compile applications outside the ports tree
should note that qt4's installation conforms to OpenBSD habits, not
TrollTech's recommendations.
Accordingly:
- libs are separated from includes.
- moc is installed as ${PREFIX}/bin/moc4, in order not to conflict 
  with other qt versions.
- uic is installed as ${PREFIX}/bin/uic4

Generally, it's just a question of invoking 

env MOC=moc4 UIC=uic4 configure --with-qt-includes=${PREFIX}/include/X11/qt4 
	--with-qt-libraries=${PREFIX}/lib/qt4

Or to force MOC/UIC in your make/gmake invocation:
make MOC=moc4 UIC=uic4
will override the Makefile contents.

Warning: the qt4 library also appears under ${PREFIX}/lib, but you
*must* make sure your application sees ${PREFIX}/lib/qt4 *first*, because
${PREFIX}/lib may also contain a later incarnation of Qt, in which case 
the linker will pick up the most recent library.