I used to download the updated versions of protoaculous from Prototype Core Google Group. Recently, Google announced that the Files section of the Google Groups will be deprecated. Also, nobody has been updating the copy of protoaculous in that group (or anywhere else on the public google-searched internet for that matter).
The instructions to create it are really simple and so you can do it yourself. You can read them at Boog Design.
For the lazy (like me), here’s the minified version of Prototype.js 1.7.0 (using the new Sizzle CSS Selector Engine – v1.0) + Scriptaculous 1.9.0:
Cached version (similar to ajax.googleapis.com versions):
Size of Prototype.js + Scriptaculous = 287,939 bytes
Size of Protoaculous.js Minified = 168,754 bytes
Packed: prototype.js + scriptaculous.js + builder.js + effects.js + dragdrop.js + controls.js + slider.js + sound.js