Manuel has written a useful set of classes to make it simpler to use postfiltering effects in OGRE, and I've collated some screenshots
posted in the forums from Manuel, supersuper and :wumpus: showing it
in action. It has been possible to use these effects in OGRE for some
time, but Manuel's work makes it a lot simpler to plug them in. The
code is available in this forum thread;
an updated version will probably be integrated into the core before the
next version since a lot of people will find it useful.