Programming Libraries

I have recently been working with a lot of javascript and php libraries and thought that I might list a few for anyone who would be interested.  From what i have been reading around the internet there seems to be a heated debate over whether or not using javascript and php libraries is a "crutch" for web developers or a just great time saving tool.  What are your thoughts?

• A nice use of Mootools transitions to create a photo viewer.
• A jquery image slider script