I’m also loving Greasemonkey for doing rapid prototyping of new UI and features. It would be neat to come up with guidelines that web applications could follow to make them more monkeyable. For example, more
ids or semantic class names.
Dive Into Greasemonkey is the best resource for getting started, and Mark Pilgrim’s later article for O’Reilly explains how to work with the native object wrappers added to Greasemonkey for security. I haven’t read the Greasemonkey Hacks book, but I may toss it in to my next Amazon order.