http://www.howtoshuffle.com and their youtube site (just search how to shuffle it should come up) I found quite useful and informative

Odds are your best bet is to look into card magic DVDs, which can often have a huge selection of impressive shuffles (riffle shuffle, one handed shuffle, etc). This kind of thing is sometimes called a "flourish" and there are a number of DVDs devoted solely to them. Some of the stuff out there is pretty technical, but there is loads of stuff for people just starting out too.