We've added a new Wikipage that gives an Introduction to the Nifty Style System:
Effect Tutorial/Introduction</a></p>
It's not completly finished yet but should give you some more informations about effects in Nifty. Additionally we've removed the old Screenshots Page from the sf.net Nifty project website and enabled the much cooler gallery feature. And there is now a sf.net standard forum enabled for the Nifty project too: