It may be going on for 4 years old now, but GPU Gems is still a fantastic resource - in fact now that you can rely on being able to use the techniques it contains on a much larger array of hardware, it’s perhaps even more practically useful than it was on release. Graphical products outside the hardcore gaming space (and this is where Ogre gets used most) are increasingly catching up and using more advanced shader effects now, and so a resource like this is actually maturing rather well.
You can imagine how pleased I was, therefore, to hear that NVIDIA and Addison Wesley have now made the whole book available for free online! That’s a fantastic offer and if you don’t have the book already you need to follow that link immediately and see what you’ve been missing. There are another 2 books in the series too of course once you’re done with that one, although for now you’ll have to reach into your pocket for those 😀