I just finished up Getting Started with Grails the free book from InfoQ by Jason Rudolph. An excellent book. Thanks Jason! I thought it was so good I decided to pay for it (even though it's free) to help support the author and InfoQ. There's a few discrepancies because the book is almost two years old and quite a bit has changed in Grails since then, but I had very few problems working through the examples with the latest version of Grails.
I'm definitely on the Groovy and Grails learning train. Both still seem very promising to me (being a Java guy) and I'm going to continue investigating both. While I set out to learn more about Ruby and Rails this year, the winds have shifted and I'm now focused on Groovy and Grails. I purchased the PDF version of Scott Davis' book Groovy Recipes and The Definitive Guide to Grails.