The wikipedia is a great free resource.
Here is a link to a grip training overview:
Wikipedia Grip Training
There is all kinds of stuff there, it is my first stop if I'm looking for something.
Hand Wrist Grip and Forearm Strength Training. Using Ironmind Captains of Crush Grippers , blobs and home made stuff. This BLOG is the rantings of a lunatic. His writings are opinion. Read at your own peril. But you will find some good training info. No fictional hand bullshit here. This is not a "grip parody" site. No Quarter Given. A Fucking Blob is a Fucking Blob - except for York "Legacy's" ;) Fuck Baraban.