This built-in YUI library is great, but the resources and code are virtually non-existent. So it seems the only options are spend weeks (if you're lucky) to learn YUI, or use jQuery.
I'd love it if Squarespace could share common scripts or examples of things that would be useful for sites.
Examples:
Lazy loading images on scroll
Endless scrolling for blogs/galleries
Sticky header on scroll
Querying JSON with AJAX
"Scroll to top" button
"Tiled" galleries like jQuery Masonry
Hidden content that appears on click