I've bought all the machine quilting titles I can find - books are another of my obsessions. ;)
The best book I've read on the subject is Machine Quilting Solutions by Christine Maraccini:
http://www.amazon.com/Machine-Quilti...228513&sr=8-11 This book helped me get beyond plain all-over meandering. It teaches you how to break the quilt down into different zones for designs and it shows each quilt with three different quilting plans from simple to complex, including trapunto.
My second favorite is Guide to Machine Quilting by Diane Gaudynski:
http://www.amazon.com/Guide-Machine-...3228513&sr=8-7
And because I love feathers so much, I also liked Hooked on Feathers by Sally Terry:
http://www.amazon.com/Hooked-Feather...3228637&sr=1-1